Video display apparatus, video viewing glasses, and system comprising the display apparatus and the glasses

ABSTRACT

Provided is a video system equipped with a video display apparatus, and video viewing glasses for use in viewing a video displayed on the video display apparatus. The video display apparatus includes: a display section for displaying a video; a synchronizing signal generator for generating an external synchronizing signal for notifying an end of displaying a frame constituting the video in synchronism with the video; and a synchronizing signal transmitter for transmitting the external synchronizing signal to the video viewing glasses. The video viewing glasses include: a synchronizing signal receiver for receiving the external synchronizing signal; an optical filter section having a pair of optical filters for adjusting amounts of light to be transmitted to a left eye and a right eye of a viewer, respectively; and an optical filter controller for controlling the optical filter section based on the external synchronizing signal.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a technology for allowing a viewer to view a video displayed on a video display apparatus through video viewing glasses, and more particularly to a technology for allowing a viewer to view a video on a video display apparatus through video viewing glasses configured to select a video displayed on the video display apparatus.

2. Description of the Related Art

A signal indicating a switching timing between videos for left and right eyes from a stereoscopic video display apparatus to liquid crystal shutter glasses may be potentially cut off for some reason. Japanese Unexamined Patent Publication No. H11-98538 discloses a technology for solving problems resulting from the signal cut-off such as disable stereoscopic viewing and screen flickering. The liquid crystal shutter glasses disclosed in Japanese Unexamined Patent Publication No. H11-98538 internally generates a signal for self-controlling the switching operation, based on a signal indicating a switching timing received from the stereoscopic video display apparatus, and controls to switch liquid crystal shutters, using the generated signal. Consequently, the switching operation of the liquid crystal shutters may be still controllable, even if the liquid crystal shutter glasses temporarily fail to receive a signal from the stereoscopic video display apparatus, thereby solving the above problem. In the case where there are plural clocks of a signal indicating a switching operation between videos for left and right eyes to be transmitted from the stereoscopic video display apparatus, the liquid crystal shutter glasses disclosed in Japanese Unexamined Patent Publication No. H11-98538 is operable to respond to the clocks.

In the case where shutters of glasses, of which response speed is so slow, in use are switched simultaneously with start of a sub-field in viewing a stereoscopic image to be provided by a PDP (Plasma Display Panel), the shutters may block light emission from the PDP. The technology disclosed in Japanese Unexamined Patent Publication No. 2000-36969 aims to solve the problem by performing a switching operation between a left eye shutter and a right eye shutter of glasses during a non-display period in a sub-field.

Japanese Unexamined Patent Publication No. H11-98538 does not disclose a technology for controlling a video display apparatus and/or video viewing glasses, taking a difference among various types of video display apparatuses (e.g. an apparatus incorporated with a CRT (Cathode Ray Tube), an apparatus incorporated with a liquid crystal element such as an LCD (Liquid Crystal Display), and a PDP) into account.

Japanese Unexamined Patent Publication No. 2000-36969 discloses the switching operation between left and right liquid crystal shutters during a non-display period in a sub-field on a PDP to be used as a video display apparatus, but does not disclose a technology for controlling a video display apparatus and/or video viewing glasses, taking an influence on video display by a video display apparatus (e.g. how the switching display between a left eye video and a right eye video affect an image to be viewed) into account .

SUMMARY OF THE INVENTION

An object of the invention is to provide an improved video viewing technology with use of a video display apparatus and video viewing glasses.

A video display apparatus according to an aspect of the invention that has accomplished the above object is adapted to display a video to be viewed through video viewing glasses. The video display apparatus includes: a display section for displaying the video; a synchronizing signal generator for generating an external synchronizing signal for notifying the video viewing glasses of an end of displaying a frame constituting the video in synchronism with the video; and a synchronizing signal transmitter for transmitting the external synchronizing signal.

Video viewing glasses according to another aspect of the invention include: a synchronizing signal receiver for receiving an external synchronizing signal for notifying an end of displaying a frame constituting a video in synchronism with the video; an optical filter section including a pair of optical filters for adjusting amounts of light to be transmitted to a left eye and a right eye of a viewer, respectively; and an optical filter controller for controlling the optical filter section based on the external synchronizing signal.

A video system according to yet another aspect of the invention is provided with a video display apparatus, and video viewing glasses for use in viewing a video displayed on the video display apparatus. The video display apparatus includes: a display section for displaying a video; a synchronizing signal generator for generating an external synchronizing signal for notifying an end of displaying a frame constituting the video in synchronism with the video; and a synchronizing signal transmitter for transmitting the external synchronizing signal to the video viewing glasses. The video viewing glasses include: a synchronizing signal receiver for receiving the external synchronizing signal; an optical filter section having a pair of optical filters for adjusting amounts of light to be transmitted to a left eye and a right eye of a viewer, respectively; and an optical filter controller for controlling the optical filter section based on the external synchronizing signal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a schematic configuration of a video system embodying the invention.

FIG. 2 is a diagram showing a hardware configuration of the video system shown in FIG. 1.

FIG. 3 is a diagram showing a functional configuration of a video display apparatus shown in FIG. 1.

FIG. 4 is a diagram showing a functional configuration of video viewing glasses shown in FIG. 1.

FIG. 5 is a diagram for describing a difference in light emitting method depending on a display system of a video displayer shown in FIG. 3.

FIG. 6 is a diagram showing an example of a video in the case where the video displayer shown in FIG. 3 displays a stereoscopic video.

FIG. 7 is a diagram exemplifying a relation between a video frame in accordance with a sub-field driving shown in FIG. 5, and a synchronizing signal.

FIGS. 8A and 8B are diagrams showing examples of a synchronizing signal to be transmitted by a transmission controller shown in FIG. 3.

FIG. 9 is a diagram exemplifying a relation between generation of a synchronizing signal by a synchronizing signal generator shown in FIG. 3, and control for an optical filter section.

FIG. 10 is a diagram showing a relation between generation of a synchronizing signal in the case where an LCD is used as the video displayer shown in FIG. 3, and control for an optical filter.

FIG. 11 is a flowchart for generating a synchronizing signal by the synchronizing signal generator shown in FIG. 3.

FIG. 12 is a diagram showing control on transmission interval among synchronizing signal groups.

FIG. 13 is a diagram showing generation of synchronizing signals, in the case where a video to be displayed on the video displayer shown in FIG. 3 is a moving picture video representing single contents.

FIG. 14 shows a video frame in a moving picture frame to be displayed on the video displayer shown in FIG. 3, where the moving picture frame represents single contents.

FIG. 15 is a diagram showing an example of a control operation for the optical filter section in transmitting three kinds of synchronizing signals having waveforms different from each other by the transmission controller shown in FIG. 3.

FIG. 16 is a diagram showing an example of a control operation in displaying a two-dimensional video on the video displayer shown in FIG. 3.

FIG. 17 is a diagram showing an example of control for the optical filter section in transmitting four kinds of synchronizing signals having waveforms different from each other by the transmission controller shown in FIG. 3.

FIG. 18 is a diagram showing an example of control in allowing a viewer to selectively view a video to be displayed on the video displayer shown in FIG. 3.

FIG. 19 is a diagram showing an example of a video to be displayed on a video display apparatus to be used in the control shown in FIG. 18.

FIG. 20 is a diagram showing an example of a video to be visually recognized by a viewer through the control shown in FIG. 18.

FIG. 21 is a diagram for describing a difference in control of video viewing glasses depending on a difference in response speed.

FIG. 22 is a diagram showing a relation between an internal signal to be generated by a synchronizing signal generator, and a synchronizing signal to be transmitted by a synchronizing signal transmitter.

DETAILED DESCRIPTION OF THE INVENTION First Embodiment

<1. Configuration on Video Display System>

FIG. 1 is a diagram showing a video display system comprising a video display apparatus, and video viewing glasses to be used in viewing a video displayed on the video display apparatus. In this embodiment, a viewer is allowed to visually recognize a stereoscopic video by viewing a video to be displayed on a display plane of the video display apparatus through the video viewing glasses.

A video display system 1 shown in FIG. 1 includes a video display apparatus 100 for displaying a video, and video viewing glasses 120. The video display apparatus 100 includes a display panel 206. A left-eye video and a right-eye video are alternately displayed on the display panel 206. The left-eye video and the right-eye video to be displayed on the video display apparatus 100 may contain contents different from each other by a parallax in the viewer's eyes.

The video viewing glasses 120 substantially looks like a vision correction eyeglasses as a whole. The video viewing glasses 120 includes an optical filter section 224. The optical filter section 224 includes a left-eye optical filter 241 disposed in front of the left eye of a viewer, and a right-eye optical filter 242 disposed in front of the right eye of the viewer, when the viewer wears the video viewing glasses 120. The video viewing glasses 120 adjust the amount of light from a video to be transmitted to the left-eye of the viewer through the left-eye optical filter 241, and the amount of light from a video to be transmitted to the right-eye of the viewer through the right-eye optical filter 242. The adjustment with respect to the amount of light from a video is synchronized with a video to be outputted to the display panel 206 of the video display apparatus 100. The viewer perceives the parallax in the videos to be viewed by the left eye and the right eye, and recognizes a video to be displayed on the video display apparatus 100, as a stereoscopic video.

A video subjected to a predetermined processing such as a processing for a stereoscopic video (3D video) is outputted from the display panel 206 of the video display apparatus 100. A synchronizing signal transmitting section 110 in the video display apparatus 100 transmits a signal (external synchronizing signal) for synchronizing a video to be outputted to the display panel 206 of the video display apparatus 100 with a control operation of the video viewing glasses 120. The video viewing glasses 120 receive the external synchronizing signal from the video display apparatus 100. The video viewing glasses 120 perform a predetermined optical processing to light to be incident into the left eye and the right eye, based on the synchronizing signal. A synchronizing signal receiving section 130 in the video viewing glasses 120 receives the synchronizing signal from the synchronizing signal transmitting section 110, and adjusts the amount of light to be transmitted to the left eye and/or the right eye, based on the synchronizing signal. Thereby, a viewer wearing the video viewing glasses 120 is allowed to properly view a video displayed on the video display apparatus 100.

FIG. 2 is a diagram showing a hardware configuration of the video display apparatus 100 and the video viewing glasses 120. The video display apparatus 100 includes a decoding IC 200, a video signal processing IC 201, a transmission control IC 202, a CPU 203, a memory 204, a clock 205, the display panel 206, and an infrared light emitting element 207.

The decoding IC 200 decodes an encoded and inputted video signal, and outputs video data in a predetermined format. The video encoding system may be MPEG (Motion Picture Experts Group)-2, MPEG-4, and H264.

The video signal processing IC 201 performs a signal processing concerning display of a stereoscopic video. The video signal processing IC 201 processes the video signal from the decoding IC 200 to display video data as a stereoscopic video. In a certain embodiment, the video signal processing IC 201 may detect a left-eye video and a right-eye video out of video data decoded by the decoding IC 200, and may alternately display the detected left-eye video and the detected right-eye video with time. In another embodiment, a left-eye video and a right-eye video may be automatically generated from video data outputted from the decoding IC 200, and the video signal processing IC 201 may alternately output the generated left-eye video and the generated right-eye video to the display panel 206. After the signal processing concerning display of a stereoscopic video, the video signal processing IC 201 generates an output signal in conformity with a signal input system of the display panel 206.

Alternatively, the video signal processing IC 201 may perform a processing other than the above processing. For instance, the video signal processing IC 201 may further adjust the hue or a video to be displayed or interpolate a video between frames of video data generated by the decoding IC 200 to increase the frame rate of a video depending on characteristics of the display panel 206.

The transmission control IC 202 generates synchronizing signals which synchronize with the left-eye video and the right-eye video generated by the video signal processing IC 201, and outputs the generated synchronizing signals to the infrared light emitting element 207, which will be described later in detail.

The CPU 203 controls the overall operations of the video display apparatus 100. The CPU 203 controls a component section included in the video display apparatus 100 (e.g. the decoding IC 200 and the video signal processing IC 201) to handle the overall operations of the video display apparatus 100. The CPU 203 may control the overall operations of the video display apparatus 100 in accordance with a program recorded in the memory 204, an input (not shown) from an external device, or the like.

The memory 204 is utilized as an area where a program to be executed by the CPU 203, or temporary data generated in the course of executing a program is recorded. A volatile RAM (Random Access Memory) or a non-volatile ROM (Read Only Memory) may be used as the memory 204.

The clock 205 supplies a clock signal, which may be used as an operation reference for the respective ICs, to the CPU 203 and the other constituent components.

The display panel 206 displays a video signal outputted from the video signal processing IC 201. Various display systems such as a conventional CRT system, and systems using an LCD with a liquid crystal element, the other PDP, and an organic electroluminescence may be applied to the display panel 206.

The infrared light emitting element 207 outputs a synchronizing signal to an external device, using infrared light under the control of the transmission control IC 202.

In this embodiment, the video display apparatus 100 and the video viewing glasses 120 are synchronized with each other by using infrared light. The invention is not limited to the above. Synchronization between the video display apparatus 100 and the video viewing glasses 120 may be established by using a wired signal, a wireless signal, an ultrasonic wave, or other transmission means.

The video viewing glasses 120 include a CPU 220, a memory 221, a clock 222, an infrared light receiving element 223, and the optical filter section 224.

The CPU 220 controls the overall operations of the video viewing glasses 120. The CPU 220 may control the video viewing glasses 120, for example, in accordance with a program recorded in the memory 221 or an input (not shown) from an external device.

The memory 221 is used as an area where data of a program to be executed by the CPU 220 is recorded, or temporary data generated in the course of executing a program is saved.

The clock 222 supplies a clock signal, which is used as an operation reference, to the other ICs constituting the video viewing glasses 120. The clock signal may be a frequency-dividing or frequency-multiplying signal as necessary.

The infrared light receiving element 223 is a light receiving section for receiving a synchronizing signal transmitted from the infrared light emitting element 207 in the video display apparatus 100.

The optical filter section 224 is disposed in front of the left eye and the right eye of a user wearing the video viewing glasses 120 to adjust the amounts of light transmitted to the left eye and the right eye. The optical filter section 224 properly operates for the light toward the left eye and the right eye under the control of the CPU 220 to impart an intended optical effect to the user wearing the glasses 120.

The hardware configuration shown in FIG. 2 is merely an example, and the invention is not limited to the above. For instance, hardware may include an integrated IC for plural ICs such as the decoding IC 200 and the video signal processing IC 201. Further alternatively, an execution process for a program by the CPU 203 may be performed, for example, by a PLD (Programmable Logic Device).

FIG. 3 is a diagram showing a functional configuration of the video display apparatus 100. The video display apparatus 100 includes a video decoder 300, an L/R signal separator 301, a stereo signal processor 302, a video displayer 303, a synchronizing signal generator 304, a transmission controller 305, and a synchronizing signal transmitter 306.

The video decoder 300 decodes an encoded and inputted video signal. The video decoder 300 corresponds to the decoding IC 200 in the hardware configuration shown in FIG. 2.

The L/R signal separator 301 generates video signals for the left eye and the right eye from a video signal decoded by the video decoder 300 or separates the video signal decoded by the video decoder 300 into video signals for the left eye and the right eye.

The stereo signal processor 302 adjusts the left-eye video signal and the right-eye video signal separated by the L/R signal separator 301, for example, in accordance with characteristics of the video displayer 303 configured to display a video to be visually recognized through the video viewing glasses 120. For instance, the stereo signal processor 302 may adjust a parallax between a left-eye video and a right-eye video in accordance with the size of a display plane of the video displayer 303. The video displayer 303 exemplarily shown in FIG. 3 as a display section corresponds to the display panel 206 illustrated in FIG. 1 and FIG. 2.

The synchronizing signal generator 304 generates a synchronizing signal in synchronism with or corresponding to the left-eye video and the right-eye video generated by the L/R signal separator 301. In the generation, the types or timing of a synchronizing signal to be generated are adjusted, for example, in accordance with the characteristics of the video displayer 303. The synchronizing signal will be described later.

The L/R signal separator 301, the stereo signal processor 302, and the synchronizing signal generator 304 correspond to the video signal processing IC 201 in the hardware configuration shown in FIG. 2.

The video displayer 303 displays a video signal processed by the stereo signal processor 302, as a video. As described above, the video displayer 303 corresponds to the display panel 206 in the hardware configuration shown in FIG. 2.

The synchronizing signal transmitter 306 transmits the synchronizing signal generated by the synchronizing signal generator 304 to the external device (video viewing glasses 120) under the control of the transmission controller 305 (to be described later). The synchronizing signal transmitter 306 corresponds to the infrared light emitting element 207 in the hardware configuration shown in FIG. 2.

The transmission controller 305 controls the data amount of a synchronizing signal to be transmitted, the data transmission interval, and the like. It will be described later how the transmission controller 305 controls them. The transmission controller 305 corresponds to the transmission control IC 202 in the hardware configuration shown in FIG. 2.

FIG. 4 is a diagram showing a functional configuration of the video viewing glasses 120. The video viewing glasses 120 include an external synchronizing signal receiver 400, a synchronizing signal detector 401, a synchronizing signal analyzer 402, a synchronizing information storage 403, an internal synchronizing signal generator 404, an optical filter controller 405, and the optical filter section 224.

The external synchronizing signal receiver 400 receives a synchronizing signal with infrared light transmitted from the video display apparatus 100. The external synchronizing signal receiver 400 converts the received infrared light into an electrical signal which is then outputted to the synchronizing signal detector 401 (to be described later). The external synchronizing signal receiver 400 corresponds to the infrared light receiving element 223 in the hardware configuration shown in FIG. 2.

The synchronizing signal detector 401 detects the synchronizing signal (electrical signal) converted from the infrared light received by the external synchronizing signal receiver 400. The synchronizing signal is detected, for example, as a signal in a predetermined electrical waveform.

The synchronizing signal analyzer 402 analyzes information such as a time interval to be used in operating the optical filter section 224 (to be described later), based on the synchronizing signal detected by the synchronizing signal detector 401. The information (such as time interval information) for operating the optical filter section 224 may include, for example, information relating to timings of opening/closing the left-eye optical filter 241 and the right-eye optical filter 242. Analysis on the information including the time interval information will be described later.

The synchronizing signal detector 401 and the synchronizing signal analyzer 402 correspond to a part of a program to be executed by the CPU 220 in the hardware configuration shown in FIG. 2.

The synchronizing information storage 403 records/stores control information relating to operation of the optical filter section 224 analyzed by the synchronizing signal analyzer 402 based on a synchronizing signal. The synchronizing signal storage 403 corresponds to the memory 221 in the hardware configuration shown in FIG. 2. The CPU 220 records the control information in the memory 221.

The internal synchronizing signal generator 404 generates a synchronizing signal within the video viewing glasses 120, based on synchronizing information recorded in the synchronizing information storage 403, or synchronizing information analyzed by the synchronizing signal analyzer 402. The internal synchronizing signal generator 404 corresponds to the CPU 220 and the clock 222 in the hardware configuration shown in FIG. 2.

The optical filter controller 405 controls operations of the left-eye optical filter 241 and the right-eye optical filter 242 of the video viewing glasses 120 (e.g. adjusting the amount of light to be transmitted through the optical filter section 224). The optical filter controller 405 corresponds to the program for controlling an optical filter to be executed by the CPU 220 in the hardware configuration shown in FIG. 2.

The optical filter section 224 includes the paired optical filters 241 and 242 for adjusting the amount of light to be transmitted and incident to the left eye and the right eye. As shown in FIG. 1, the paired optical filters 241 and 242 are mounted on the video viewing glasses 120. The optical filters 241 and 242 include various kinds of filters such as a filter for adjusting the amount of light to be transmitted, and a filter for adjusting the polarization of light to be transmitted. The optical filters 241 and 242 may further include a liquid crystal element to be controlled so as to adjust the amount of light to be transmitted thereto. The optical filter section 224 in the hardware configuration shown in FIG. 2 is indicated with the same reference numeral as in FIG. 1.

In this embodiment, a video to be displayed on the video display apparatus 100 includes a left-eye video and a right-eye video. The left-eye video and the right-eye video are alternately switched. The left-eye optical filter 241 and the right-eye optical filter 242 of the optical filter section 224 are operated like shutters for alternately decreasing and increasing the amounts of light to be transmitted therethrough. The operation to be performed by the optical filter section 224 is not limited to the operation in this embodiment. As another example of the operation to be performed by the optical filter section 224, the left-eye optical filter and the right-eye optical filter may be operated so as to change their polarizing directions. All kinds of the optical filters 241 and 242 capable of adjusting the amounts of light to be transmitted in synchronism with a switching operation of displaying a video frame may be applied to the optical filter section 224.

The invention is not limited to the functional arrangements shown in FIGS. 3 and 4. For instance, in the description referring to FIGS. 3 and 4, the synchronizing signal transmitter 306 and the video displayer 303 is included in the video display apparatus 100. Alternatively, the synchronizing signal transmitter 306 and the video displayer 303 may be provided in individual apparatuses, respectively. For instance, a video display apparatus having a function of merely displaying a video, and a synchronizing signal transmitting device for transmitting and outputting a synchronizing signal may be provided as individual apparatuses.

FIGS. 2 through 4 shows merely an example of correlation between the hardware configuration and the functional configuration to describe this embodiment, and the invention is not limited to the above. Other hardware configurations and other functional configurations may be applied to the invention.

<2. Synchronizing System in Accordance with Characteristic of Video Displayer>

FIG. 5 is a diagram for describing a difference in light emitting method depending on a display system of the video displayer 303. FIG. 6 is a diagram showing example of videos to be displayed in a left-eye frame and a right-eye frame shown in FIG. 5. The video display apparatus 100 displays a video on the video displayer 303. The characteristics of the video displayer 303 greatly differ depending on a display system to be used in the display section. FIG. 5 shows display characteristics in the case where a PDP is used as the video displayer 303 (display panel 206), and display characteristics in the case where an LCD is used as the video displayer 303 (display panel 206). The section (A) in FIG. 5 shows that a frame for a left-eye video and a frame for a right-eye video are alternately and switchingly displayed in order that the video display apparatus 100 displays a stereoscopic video. FIG. 5 shows that a left-eye frame and a right-eye frame are alternately displayed on the display panel 206, in order to clarify the description. However, the invention is not limited to the above. For instance, a display system may switch a left-eye frame with a right-eye frame every several frames.

FIG. 6 is a diagram showing an example of videos for the left-eye frame and the right-eye frame shown in FIG. 5 to be displayed on the display panel 206. The upper display panel 206 in FIG. 6 displays the video for the left-eye frame and the lower display panel in FIG. 6 displays the video for the right-eye frame. Although the objects “A” displayed in both of the frames are identical to each other, display positions and viewing angles of the objects “A” on the display panels 206 are slightly different from each other. The differences in the display positions and the viewing angles may be defined as a difference in contents by a parallax in the viewer's eyes between a video in the left-eye frame and a video in the right-eye frame. The object “A” in FIG. 6 is spherical to simplify the description, and a difference in shape is not recognized between the left-eye frame and the right-eye frame. However, the shape of an object to be displayed in the left-eye frame may be different from the shape of an object to be displayed in the right-eye frame by the amount of a parallax depending on the shape of the object “A”. FIG. 6 clearly describes the difference in display contents corresponding to a parallax between the left-eye frame and the right-eye frame but it should be noted that the other difference between videos which are supposed to be visually recognized by the left eye and by the right eye may be included in the difference in contents corresponding to a parallax. The difference in display contents corresponding to a parallax between the left-eye frame and the right-eye frame shown in FIG. 6 is shown to clarify the description. It should be noted that the other difference between a video which is supposed to be visually recognized by the left eye, and a video which is supposed to be visually recognized by the right eye is included in the contents difference corresponding to a parallax.

Referring back to FIG. 5, the section (B) in FIG. 5 shows light emission amounts in the case where a PDP is used as the video displayer 303. In the light emitting with the PDP, light emitting periods (called as sub-fields) obtained by time-dividing a frame are used. The gradations of a frame are adjusted by combining light emission amounts different from each other within the respective sub-fields. Discharged amounts 500 represented by bars in the bar graph in FIG. 5 correspond to light emission amounts of the video displayer 303 in the respective sub-fields. A light emission amount 501 indicated by the curve in FIG. 5 represents a time-variation in light emission amounts of individual pixels in the video displayer 303. The light emission amount 501 of the video displayer 303 slightly delays with respect to the discharged amounts 500 in the respective sub-fields. The delay may, for example, result from response characteristics of fluorescent elements, which are sealed in the respective pixels, at the time of turning on the pixels or afterglow characteristics of the fluorescent elements at the time of turning off the pixels

In the case where a PDP is used as the video displayer 303 (display panel 206), preferably, the synchronizing signal generator 304 shown in FIG. 3 may generate and transmit a synchronizing signal, taking such display characteristics of the video displayer 303 into account. In the case where a PDP is used as the video displayer 303, as described above, there is a time lag between an input signal to be used in light emission for a sub-field and actual light emission of a fluorescent element, for instance. In particular, as indicated by the light emission amount 501 represented by a curve, a part of light emission in the left-eye frame which lies in the right-eye frame becomes an afterglow (crosstalk) which affects light emission in the right-eye frame. The afterglow greatly affects stereoscopic video display. If a video in the left-eye frame remains as an afterglow in a video in the right-eye frame, the viewer may recognize an afterglow of the left-eye frame as a part of the video in the right-eye frame while viewing the video in the right-eye frame (in other words, a video in the left-eye frame visually affects a video to be recognized by the right eye). As a result, the video display apparatus 100 may provide the viewer, who views a video through the video viewing glasses 120, with an unclear stereoscopic video.

The section (C) in FIG. 5 shows display characteristics of the video displayer 303 in the case where an LCD is used as the video displayer 303 (display panel 206). Similarly to a CRT and so on, an LCD successively controls the respective pixels along a scanning line (an area indicated by the numeral 502 means that a screen is being scanned (a video is being written over)) to display a video on a display plane. Because of the display characteristics of the LCD, while the pixels are being scanned, a video before scanning and an updated video after scanning coexist on the display plane of the LCD (a video is distorted). In particular, in the case where a left-eye video and a right-eye video are alternately displayed in stereoscopic video viewing, the coexistence of left-eye video and the right-eye video during a scanning operation distorts a video. As a result, the video display apparatus 100 may provide the viewer, who views a video through the video viewing glasses 120, with an unclear stereoscopic video.

FIG. 7 is a diagram showing an example of generating a synchronizing signal, in the case where a PDP is used as the video displayer 303. The synchronizing signal generator 304 in this example generates a synchronizing signal, taking characteristics of the video displayer 303 into account.

The section (A) in FIG. 7 shows a video to be displayed on the video displayer 303. Similarly to the description referring to FIGS. 5 and 6, in the example shown in FIG. 7, a video in a left-eye frame and a video in a right-eye frame are alternately displayed. The section (B) in FIG. 7 shows synchronizing signals (pulses) to be generated and transmitted in synchronism with a video to be displayed on the video displayer 303.

The section (C) in FIG. 7 shows an example of controlling the amount of light to be transmitted from the PDP (i.e. the video displayer 303) in accordance with a synchronizing signal from the video display apparatus 100 shown in the section (B) in FIG. 7. The video displayer 303 controls light emission for sub-fields corresponding to a video in the left-eye frame and a video in the right-eye frame to display the video corresponding to the left-eye frame and the video corresponding to the right-eye frame. As a result of the control operation, light is emitted on the display plane of the video displayer 303 as shown by a graphical curve 711 based on a video signal. In this case, a video in one of the frames may affect a video in the other of the frames. In the example shown in FIG. 7, an afterglow in the left-eye frame may affect the right-eye frame while an afterglow in the right-eye frame may affect the left-eye frame.

The synchronizing signal generator 304 controls a synchronizing signal to be transmitted to the video viewing glasses 120 to prevent these afterglows from affecting on video viewing. The synchronizing signal generator 304 generates a signal operable to properly control the optical filter section 224 of the video viewing glasses 120. The synchronizing signal generator 304 controls a synchronizing signal so that an afterglow in the left-eye frame may not affect viewing the right-eye frame, and that an afterglow in the right-eye frame may not affect viewing the left-eye frame. The synchronizing signal generator 304 generates a synchronizing signal in association with display characteristics (e.g. response characteristics at the time of turning on the pixels, or afterglow characteristics at the time of turning off the pixels) of the video displayer 303, so that the left-eye optical filter 241 and the right-eye optical filter 242 of the optical filter section 224 in the video viewing glasses 120 are controlled based on the synchronizing signal.

The section (B) in FIG. 7 shows an example of synchronizing signals (pulses) to be generated by the synchronizing signal generator 304. The synchronizing signal generator 304 generates synchronizing signals for controlling the optical filter section 224 in the video viewing glasses 120 in correspondence to start (the first light emission of sub-fields in one frame) and end (the last light emission of sub-fields in the one frame) of a display frame.

This embodiment may be characterized in generating a synchronizing signal for controlling the video viewing glasses 120 at a point of time when a display frame is ended, in addition to the point of time when the display frame is started, in order to control the optical filter section 224. In the case where a synchronizing signal is outputted merely at a point of time when a display frame is started, the influence by afterglow may not be sufficiently suppressed. The optical filter section 224 may not instantaneously respond to a synchronizing signal, and it may take a certain time to open/close the filter. In the case where only a synchronizing signal at a point of time when a display frame is started is used for controlling the optical filter section 224 at a single timing, a video on the video displayer 303, which is not originally intended, may be inadvertently recognized by an eye of the viewer during an opening/closing time of the filter. As will be described later, it is necessary to transmit a synchronizing signal at a point of time when a display frame is ended, in addition to the point of time when the display frame is started to avoid the above drawbacks. There is also proposed a well-known approach, wherein a synchronizing signal is transmitted from the synchronizing signal transmitter 306 at either one of start timing and end timing of a display while the video viewing glasses 120 measure a time with the internal clock 222 to automatically shift timings of light blocking operation and light transmitting operation of the optical filter section 224. However, such well-known approach may not be applicable to various display characteristics of display devices, as will be described later.

FIG. 8 is a diagram showing an example of a first synchronizing signal 700 and/or 701, and a second synchronizing signal 702 and/or 703 shown in FIG. 7. As shown in FIG. 7, in this embodiment, the first synchronizing signal 700, 701, and the second synchronizing signal 702, 701 are received by the external synchronizing signal receiver 400, as synchronizing signals.

The synchronizing signals received by the external synchronizing signal receiver 400 are transmitted to the synchronizing signal analyzer 402 via the synchronizing signal detector 401. The synchronizing signal analyzer 402 discriminates the first synchronizing signal 700, 701 from the second synchronizing signal 702, 703. In the example shown in FIG. 7, the first synchronizing signal 700, 701 is recorded in the synchronizing information storage 403 as a signal to be used for controlling the left-eye optical filter 241 to be opened/closed. The second synchronizing signal 702, 703 is recorded in the synchronizing information storage 403 as a signal to be used for controlling the right-eye optical filter 242 to be opened/closed. The internal synchronizing signal generator 404 reads out a signal recorded in the synchronizing signal storage 403, and then generates an internal synchronizing signal for controlling the optical filter section 224 with the optical filter controller 405.

As shown in FIG. 8A, the pulse number in a predetermined time differs between the first synchronizing signal 700, 701, and the second synchronizing signal 702, 703 to be used in this embodiment. The synchronizing signal analyzer 402 may discriminate the first synchronizing signal 700, 701 from the second synchronizing signal 702, 703 based on the difference in the pulse number. Also, in the example shown in FIG. 7, the synchronizing signal analyzer 402 discriminates the synchronizing signal 701, 703, which is transmitted at a later time, out of the successively transmitted two synchronizing signals having an identical waveform, as a synchronizing signal for closing the optical filter. As shown in FIG. 8B, in this embodiment, it may depend on a difference in a pulse widths between the first synchronizing signal 700, 701, and the second synchronizing signal 702, 703 that the first synchronizing signal 700, 701 is discriminated from the second synchronizing signal 702, 703. Further alternatively, in this embodiment, it may be depend on a difference in waveform other than the pulse number and the pulse width between the first synchronizing signal 700, 701, and the second synchronizing signal 702, 703 that the first synchronizing signal 700, 701 is discriminated from the second synchronizing signal 702, 703.

Referring back to FIG. 7, the synchronizing signal generator 304 generates the synchronizing signal 700, 702 for increase in the amount of light to be transmitted through the optical filter section 224 (open the optical filter section 224) at a timing when an influence of afterglow in a preceding frame is reduced after light emission for a sub-field is started. In this embodiment, a timing when an influence of afterglow is reduced means a point of time when an afterglow in the preceding frame becomes lower than a predetermined threshold value; or means a condition that an influence of afterglow is relatively reduced because of starting light emission for a sub-field in the succeeding frame (i.e. a condition that the ratio of afterglow with respect to the light emission amount becomes equal or lower than a predetermined threshold value) even if there remains an afterglow of the preceding frame. The present invention may not be limited to the above-mentioned method. Other methods may be used to evaluate and measure the afterglow. Any method for generating a synchronizing signal based on an influence by afterglow may be applied to this embodiment.

The embodiment is described in detail referring to FIG. 9. The synchronizing signal generator 304 generates a first synchronizing signal 900 for opening the left-eye optical filter 241 of the optical filter section 224 (increasing the amount of light to be transmitted through the left-eye optical filter 241) in correspondence to start of displaying a left-eye frame. In the left-eye frame shown in the sections (B) and (C) in FIG. 9, the synchronizing signal generator 304 generates the first synchronizing signal 900 before the first light emission of sub-fields in the left-eye frame is started. Upon completion of light emission for all the sub-fields in the left-eye frame, the synchronizing signal generator 304 generates a succeeding first synchronizing signal 901 for closing the left-eye optical filter 241 (decreasing the amount of light to be transmitted through the left-eye optical filter 241). By the point of time when the last light emission of sub-fields in the left-eye frame has been completed, the synchronizing signal generator 304 generates the succeeding first synchronizing signal 901. Then, the left-eye optical filter 241 of the optical filter section 224 performs an operation indicated by the left-eye frame in the section (D) of FIG. 9. Thus, the left-eye optical filter 241 is opened (the amount of light to be transmitted becomes relatively large) during a period from the first synchronizing signal 900 to the succeeding first synchronizing signal 901, so that the viewer is allowed to visually recognize a video in the left-eye frame. In the example shown in FIG. 9, the first synchronizing signal 900 to be transmitted for the first time during a period when a video in the left-eye frame is displayed functions as a synchronizing signal for increasing the amount of light of a video to be transmitted through the left eye; and the first synchronizing signal 901 to be transmitted next functions as a synchronizing signal for decreasing the amount of light of a video to be transmitted through the left eye.

By the light emission for the sub-fields in the left-eye frame, the display panel 206 (i.e. the video displayer 303) is operable to emit light of a video, as shown by a graphical curve 911. Generally, the light emission 911 indicated by the curve in FIG. 9 delays with respect to driving of a sub-field 910. The light emission 911 in the left-eye frame may remain as an afterglow 912 in the right-eye frame, for example, attribute to a display system, a display device or display characteristics of the video displayer 303. The afterglow 912 adversely affects video viewing for the left-eye frame. In the case where the synchronizing signal generator 304 generates a second synchronizing signal to be used in controlling opening the right-eye optical filter 242 simultaneously or successively with generation of the first synchronizing signal 901 to be used in controlling closing the left-eye optical filter 241, the afterglow 912 may be likely to affect light emission in the right-eye frame, so that the viewer is obstructed from properly viewing a video to be displayed on the video display apparatus 100.

In this embodiment, opening/closing the left-eye optical filter 241 and the right-eye optical filter 242 are individually and independently controlled, in place of simultaneously switching the amounts of light to be transmitted through the left-eye optical filter 241 and the right-eye optical filter 242 of the optical filter section 224 in synchronism with a switching operation between the left-eye frame and the right-eye frame, to suppress an influence of afterglow on the display panel 206 on video viewing. In this embodiment, there is a blind period that both of the left-eye optical filter 241 and the right-eye optical filter 242 are closed from the point of time when one of the optical filters is closed (to suppress the amount of light to be transmitted) to the point of time when the other of the optical filters is opened (to increase the amount of light to be transmitted). The afterglow may not affect video viewing for the viewer at all because both of the left-eye optical filter 241 and the right-eye optical filter 242 are closed in the blind period so that the viewer may not visually recognize a video in this blind period.

The synchronizing signal generator 304 generates synchronizing signals for individually and respectively opening/closing the left-eye optical filter 241 and the right-eye optical filter 242, in place of generating a synchronizing signal to be generated in a conventional control of simultaneously switching opening/closing the left-eye optical filter 241 and the right-eye optical filter 242 of the optical filter section 224. The video display apparatus 300 generates synchronizing signals (pulses) for closing the left-eye optical filter 241 and the right-eye optical filter 242, and the video viewing glasses 120 generates internal synchronizing signals corresponding to the synchronizing signals, with use of the internal synchronizing signal generator 404. The optical filter controller 405 controls the subject optical filter 241, 242 based on the internal synchronizing signal, to decrease the amount of light to be transmitted. Thereby, during a period of switching between the left-eye frame and the right-eye frame, the video viewing glasses 120 is operable to create a blind condition that the left-eye optical filter 241 and the right-eye optical filter 242 of the optical filter section 224 are closed (the amounts of light to be transmitted through the left-eye optical filter 241 and the right-eye optical filter 242 are suppressed). Accordingly, closing the left-eye optical filter 241 and the right-eye optical filter 242 of the optical filter section 224 in the video viewing glasses 120 in accordance with a synchronizing signal for closing the optical filter section 224 may prevent the viewer from viewing an afterglow on the video displayer 303, or a video in which an afterglow of a video in a preceding frame and light of a video in a succeeding frame coexist.

The synchronizing signal generator 304 is also operable to synchronize a blind period when the left-eye optical filter 241 and the right-eye optical filter 242 of the optical filter section 224 are closed, with a period when afterglow occurs at the time of switching frames on the video displayer 303 by adjusting a timing of generating a synchronizing signal. The video viewing glasses 120 controls the optical filter section 224 based on the synchronizing signal. Thereby, the viewer is allowed to view a video with a reduced influence of afterglow.

In this embodiment, the synchronizing signal generator 304 generates a synchronizing signal for closing the optical filter section 224 simultaneously with completion of light emission for the last sub-field among sub-fields in a frame. The invention is not limited to the above. Alternatively, a synchronizing signal for closing the optical filter section 224 may be generated at a timing of switching from the left-eye frame to the right-eye frame shown in the section (A) in FIG. 7. In the alternative embodiment, the synchronizing signal generator 304 may be also operable to generate a synchronizing signal for opening one of the left-eye optical filter 241 and the right-eye optical filter 242 after an influence of afterglow becomes equal to or lower than a predetermined threshold value.

As further yet another embodiment, the synchronizing signal generator 304 may generate a synchronizing signal for closing the optical filter section 224 before light emission for a sub-field in the succeeding frame (right-eye frame) is started if an afterglow in the preceding frame (left-eye frame) becomes equal to or lower than a predetermined threshold value.

Further, in the case where an operation of the left-eye optical filter 241 and/or the right-eye optical filter 242 of the optical filter section 224 is slow (response is poor), for example, as shown by a second synchronizing signal 903, the synchronizing signal generator 304 may generate a synchronizing signal for closing the optical filter section 224 before the point of time when light emission for the last sub-field among sub-fields in a frame is started. In this case, the optical filter section 224 is actually closed after light emission for all the sub-fields in the frame is ended because the operation speed (characteristics) of the optical filter section 224 is taken into account.

In this embodiment, the synchronizing signal generator 304 generates a synchronizing signal for opening the left-eye optical filter 241 and/or the right-eye optical filter 242 of the optical filter section 224 (increasing the amount of light to be transmitted) corresponding to start of a frame, before the point of time when light is turned on for sub-field driving. The invention is not limited to the above. For instance, in the case where an influence of afterglow in a preceding frame is large, as shown by a second synchronizing signal 902, the synchronizing signal generator 304 may generate a synchronizing signal for opening the right-eye optical filter 242 after light emission for a sub-field in a succeeding frame (right-eye frame) is started. Thus the influence of afterglow from the preceding frame (left-eye frame) may be advantageously reduced. As a result, the viewer may visually recognize a video in the right-eye frame, with a reduced influence of afterglow. Thereafter, the second synchronizing signal 903 is transmitted again before the point of time when the left-eye optical filter 241 is opened, whereby a blind condition that both of the left-eye optical filter 241 and the right-eye optical filter 242 are closed is created.

Referring back to FIG. 7, the section (D) and the section (E) in FIG. 7 show changes in the amount of light to be transmitted, which are obtained as a result of the control according to the above description. The section (D) in FIG. 7 shows the amount of light to be transmitted through the left-eye optical filter 241, in the case where the left-eye optical filter 241 of the optical filter section 224 in the video viewing glasses 120 is operated in accordance with a synchronizing signal generated by the synchronizing signal generator 304. The section (E) in FIG. 7 shows the amount of light to be transmitted through the right-eye optical filter 242, in the case where the right-eye optical filter 242 of the optical filter section 224 in the video viewing glasses 120 is operated in accordance with a synchronizing signal generated by the synchronizing signal generator 304. In the example shown in the section (D) and the section (E) in FIG. 7, control of closing the optical filter section 224 of the video viewing glasses 120 is performed in synchronism with a period from the point of time when the first synchronizing signal 701 is generated to the point of time when the second synchronizing signal 702 is generated, and a period from the point of time when the second synchronizing signal 703 is generated to the point of time when the first synchronizing signal 704 is generated, whereby the amounts of light to be transmitted to both eyes during these periods when an influence of afterglow is large is suppressed. Thereby, an influence of afterglow on video viewing may be suppressed.

A video viewer may view a video with a reduced influence of afterglow by synchronizing the blind period when the left-eye optical filter 241 and the right-eye optical filter 242 of the video viewing glasses 120 are closed with a period when an influence of afterglow resulting from switching between a left-eye video and a right-eye video on the video displayer 303 of the video display apparatus 100 occurs. Thereby, the video viewer may view a stereoscopic video in a preferable condition.

Solely two kinds of synchronizing signals used for synchronizing timings of starting and ending each of a left-eye video frame and a right-eye video frame to be displayed by the video display apparatus 100 with timings of opening and closing the left-eye optical filter 241 and/or the right-eye optical filter 242 of the optical filter section 224 in the video viewing glasses 120 may simplify the configuration for the viewer to view a stereoscopic video.

The synchronizing signal 701, 703 for closing the optical filter section 224 selectively gives the viewer a video free from an influence of afterglow among the frames to be displayed on the video displayer 303, so that the viewer may view a clear video.

In the embodiment, described is a method for generating a synchronizing signal in accordance with timings of starting and ending a frame. In the control for the operation of opening/closing the optical filter section 224, the timing of starting a frame may be defined as a point of time when an actual light emission indicated, for example, by the graphical curve 711 becomes not smaller than a predetermined light emission amount after light emission is performed in each of the sub-fields to display a video on the video displayer 303, and the timing of ending a frame may be defined as a point of time when an afterglow of the video to be displayed on the video displayer 303 becomes not larger than a predetermined light emission amount. In performing the above control operation, the synchronizing signal generator 304 may generate a synchronizing signal for starting a view (increasing the amount of light to be transmitted) if a video to be displayed on the video displayer 303 satisfies a predetermined quality (image quality) and may generate a synchronizing signal for ending the view (decreasing the amount of light to be transmitted) if a video to be displayed on the video displayer 303 does not satisfy the predetermined quality (image quality). Thus, the synchronizing signal generator 304 is operable to generate a synchronizing signal, based on the quality (image quality) of a video.

FIG. 10 is a diagram showing an example of generating synchronizing signals, in the case where an LCD is used as the video displayer 303. The section (A) in FIG. 10 shows a video system of the video displayer 303. Similarly to the example described referring to FIG. 9, wherein a PDP is used as the video displayer 303, in this example, a left-eye frame and a right-eye frame are alternately displayed. The section (B) in FIG. 10 is a graph showing an example of synchronizing signals (pulses) to be generated by the synchronizing signal generator 304, in the case where an LCD is used as the video displayer 303.

The section (C) in FIG. 10 shows an example of a video to be displayed on the LCD (i.e. the video displayer 303). The video displayer 303 using an LCD successively scans a video plane in accordance with a scanning line, which is a different point of the display system from a PDP. Areas 1004 and 1005 in the section (C) in FIG. 10 indicate portions where a video is scanned. Videos in a frame before scanning and after scanning coexist in the portion where a video is scanned. Accordingly, a video in the course of changing is displayed on the video plane of the video displayer 303 during the scanning operation. Thus the viewer may view the video including a disordered image or a blurred image.

In view of the above, in the case where an LCD is used as the video displayer 303, the synchronizing signal generator 304 generates a synchronizing signal as shown in the section (B) in FIG. 10. Specifically, the synchronizing signal generator 304 generates a synchronizing signal for simultaneously decreasing the amounts of light to be transmitted through the left-eye and the right-eye optical filters of the optical filter section 224 in the video viewing glasses 120 during the period when a video is scanned (e.g. the period corresponding to the area 1004). Specifically, in the case where a video shown in the section (C) in FIG. 10 is scanned, the synchronizing signal generator 304 generates a synchronizing signal 1000 for increasing the amount of light to be transmitted through the left-eye optical filter 241 after scanning of the area 1004 in the left-eye frame is ended, and then generates a synchronizing signal 1001 for decreasing the amount of light to be transmitted through the left-eye optical filter 241 before scanning of the right-eye frame succeeding the left-eye frame is started. Similarly to the control for the left-eye frame, the synchronizing signal generator 304 generates a synchronizing signal 1002 for increasing the amount of light to be transmitted through the right-eye optical filter 242 after scanning of the right-eye frame is completed, and then generates a synchronizing signal 1003 for decreasing the amount of light to be transmitted through the right-eye optical filter 242 before scanning of the left-eye frame succeeding the right-eye frame is started. The synchronizing signals generated by the synchronizing signal generator 304 are transmitted from the synchronizing signal transmitter 306 at a timing correlated to the above control operation for the video displayer 303.

The section (D) and the section (E) in FIG. 10 show an example of an operation control for the optical filter section 224, in the case where the video viewing glasses 120 receive the synchronizing signals shown in the section (B) in FIG. 10 from the synchronizing signal generator 304, the synchronizing signal transmitter 306, and the like in the video display apparatus 100. The optical filter controller 405 in the video viewing glasses 120 controls the optical filter section 224, based on the synchronizing signals received from the video display apparatus 100. The optical filter controller 405 in the video viewing glasses 120 increases/decreases the amounts of light to be transmitted by controlling the left-eye optical filter 241 and the right-eye optical filter 242 in synchronism with the synchronizing signals 1000 and 1002 for starting the respective frames. In the example shown in the section (D) and the section (E) in FIG. 10, the amount of light to be transmitted through the left-eye optical filter 241 is increased in correspondence to the synchronizing signal 1000 indicating a start of viewing a left-eye frame. Thereafter, the amount of light to be transmitted through the left-eye optical filter 241 is decreased in correspondence to the synchronizing signal 1001 indicating an end of viewing the left-eye frame. Subsequently, similarly to the control on the left-eye frame, the amount of light to be transmitted through the right-eye optical filter 242 is increased and then decreased in correspondence to the synchronizing signals 1002 and 1003 respectively indicating a start and an end of viewing the right-eye frame. The optical filter controller 405 controls the optical filter section 224 to open the left-eye optical filter 241 based on the synchronizing signal 1000, and close the left-eye optical filter 241 based on the synchronizing signal 1001. Similarly to the control on the left-eye optical filter 241, the optical filter controller 405 controls the optical filter section 224 to open the right-eye optical filter 242 based on the synchronizing signal 1002, and close the right-eye optical filter 242 based on the synchronizing signal 1003.

In the example shown in FIG. 10, the synchronizing signal generator 304 generates the synchronizing signals 1000 and 1002 at a point of time when scanning of the respective frames is ended, and generates the synchronizing signals 1001 and 1003 before scanning of the respective succeeding frames is started. The optical filter controller 224 controls the optical filter section 224 in synchronism with the synchronizing signals 1000, 1001, 1002, and 1003. Thereby, the optical filter controller 405 is operable to increase/decrease the amounts of light to be transmitted to both eyes in synchronism with a video to be displayed on the video displayer 303 of the video display apparatus 100. In particular, the optical filter controller 405 controls the optical filter section 224 to close both of the left-eye and the right-eye optical filters while a video is scanned so as to prevent the viewer from viewing an undesirable video such as a disordered image or a blurred image on the video displayer 303, thereby allowing the viewer to view a video of enhanced quality.

As described above, even in a case that an LCD is used as the video displayer 303, based on the video displayer 303 in the video display apparatus, the optical filter section 224 in the video viewing glasses 120 is controlled to be synchronized with the video displayer 303, thereby allowing the viewer to view a clear stereoscopic video through the LCD display.

Solely two kinds of synchronizing signals used for controlling the optical filter section 224 in the video viewing glasses 120 to be synchronized with a left-eye video and a right-eye video to be displayed on the video display apparatus 100 may result in relatively simplified the configuration for the viewer to view a stereoscopic video.

In the case where an LCD is used as the video displayer 303, scanning speed for overwriting a video may go up as the temperature of a liquid crystal element increases. Therefore a timing of generating a synchronizing signal indicating a start of viewing a video frame may be determined based on a required time for a scanning operation through a dynamic calculation with a detected temperature of a liquid crystal element by a temperature sensor. In the section (C) in FIG. 10, the scanning area 1006, 1007 of a video means a shortened scanning time because of a higher response speed resulting from an increase in the temperature of the liquid crystal element, so that the synchronizing signal generator 304 speeds up a timing of generating a synchronizing signal indicating a start of viewing a video (see the section (B) in FIG. 10).

The temperature of a liquid crystal element may be directly detected with a temperature sensor or indirectly detected through logical calculation for the temperature of the liquid crystal element, for example, based on an operation time of a backlight device which may affect the temperature of the liquid crystal element. In other words, the synchronizing signal generator 304 may be operable to dynamically determine the timing of generating a synchronizing signal for notifying start of viewing a video, based on temperature information calculated by any method.

Preferably, the backlight device of the LCD is turned off, or is lit dimly, while the LCD (i.e. the video displayer 303) overwrites a video (scans a video), which decreases the amount of light to be irradiated from the display plane of the LCD, so that it is less likely that the viewer may view a video under scanning operation, thereby allowing the viewer to view a stereoscopic video with enhanced quality.

FIG. 11 is a flowchart showing a control of generating a synchronizing signal by the video display apparatus 100, based on display characteristics of the video displayer 303.

In Step 1101 (S1101), the synchronizing signal generator 304 acquires display characteristics of the video displayer 303. The video display apparatus 100 stores in advance, for example, in the memory 204, information relating to display characteristics of the video displayer 303, for example, information indicating that the display system is of PDP or LCD, information relating to afterglow, and information relating to a scanning operation. The synchronizing signal generator 304 acquires the information relating to display characteristics of the video displayer 303, which is stored, for example, in the memory 204.

In the case where a PDP is used as the video displayer 303 in a certain embodiment, the synchronizing signal generator 304 acquires information relating to afterglow characteristics inherent to the PDP to be used. In the case where an LCD is used as the video displayer 303, the synchronizing signal 304 acquires, for example, information relating to a time required for a scanning operation.

In Step 1102 (S1102), the synchronizing signal generator 304 acquires a frame rate of a video to be displayed. The frame rate of a video is obtainable based on video information decoded by the video decoder 300 or information stored in the L/R signal separator 301 or the memory 204.

In Step 1103 (S1103), the method for generating a synchronizing signal (generating a synchronizing signal corresponding to afterglow or video scanning) is determined, based on the characteristics of the video displayer 303 acquired in S1101. In the above embodiment, it is determined whether the synchronizing signal generator 304 should generate a synchronizing signal corresponding to afterglow or video scanning. For instance, in the case where a signal to be transmitted to the synchronizing signal generator 304 is a signal generated in using a PDP as the video displayer 303, it is determined that the synchronizing signal generator 304 should generate and transmit the synchronizing signals 901 and 903 (see FIG. 9) in correspondence to ending of a left-eye video frame and a right-eye video frame, respectively. In the case where a signal to be transmitted to the synchronizing signal generator 304 is a signal generated in using an LCD as the video displayer 303, it is determined that the synchronizing signal generator 304 should generate and transmit the synchronizing signals 1000 and 1002 in correspondence to scanning of a left-eye video frame and a right-eye video frame, respectively.

In the case where it is determined that the synchronizing signal generator 304 should generate and transmit the synchronizing signals 901 and 903 in correspondence to ending of a left-eye video frame and a right-eye video frame (in correspondence to the afterglow characteristics) respectively, Step 1104 is executed. In Step 1104 (S1104), the synchronizing signal generator 304 generates the synchronizing signals 901 and 903 at the timings of ending the respective video frames, based on the determination in S1103. In this case, as described above, the synchronizing signal generator 304 calculates, for example, timings of generating the synchronizing signals 901 and 903, based on, for example, the afterglow characteristics of the video displayer 303, and generates the synchronizing signals 901 and 903 based on, for example, the calculated timings.

In the case where it is determined that the synchronizing signal generator 304 should generate and transmit the synchronizing signals 1000 and 1002 in correspondence to scanning of a left-eye video frame and a right-eye video frame (in correspondence to video scanning) respectively, Step 1105 is executed. In Step 1105 (S1105), the synchronizing signal generator 304 generates the synchronizing signals 1000 and 1002 at the timings of completing scanning of the respective video frames.

As described above, the video display apparatus 100 generates and transmits synchronizing signals based on the display characteristics of the video displayer 303. The video viewing glasses 120 allows the viewer to view a clear video by controlling the optical filter section 224 based on the synchronizing signals from the video display apparatus 100.

The left-eye frame and the right-eye frame may have identical video characteristics to each other. However, the embodiment is not limited to the above. For instance, in the case where the left-eye frame and the right-eye frame have different video characteristics from each other, the synchronizing signal generator 304 may generate synchronizing signals of which waveforms are different from each other in the left-eye frame and the right-eye frame, based on the respective video characteristics so that the optical filter controller 405 differently controls the left-eye optical filter 241 and the right-eye optical filter 242, based on the synchronizing signals of which waveforms are different from each other. In this case, as described in the embodiment referring to the section (D) and the section (E) in FIG. 7, the synchronizing signals 700 and 701 for the left-eye frame, and the synchronizing signals 702 and 703 for the right-eye frame are independently generated, respectively.

In this embodiment, described is an example, wherein the display characteristics of the display section is the afterglow characteristics (characteristics that a video in a preceding frame is visually recognized after the video in the preceding frame is switched over to a video in a succeeding frame) or the characteristics relating to a scanning operation at the time of switching videos. The invention is not limited to the above. For instance, generation of a synchronizing signal may be controlled depending on the other display characteristics (e.g. response characteristics of a light emitting element) of the display section. Any method for generating and controlling synchronizing signals depending on display characteristics of the video displayer 303 is applicable to the invention.

In this embodiment, two kinds of synchronizing signals are shown, wherein one of the two kinds of synchronizing signals indicates a synchronizing signal to be used in a control operation of opening an optical filter for increasing the light amount, and the other one of the two kinds of synchronizing signals indicates a synchronizing signal to be used in a control operation of closing an optical filter for decreasing the light amount. These synchronizing signals may be respectively used as synchronizing signals for notifying a start and an end of displaying a video frame. As described above, the optical filter controller 405 in the video viewing glasses 120 may control the left-eye optical filter 241 and the right-eye optical filter 242 of the optical filter section 224, based on synchronizing signals indicating a start and an end of displaying a frame.

<3. Synchronizing System using Internal Synchronization>

In the foregoing embodiment, the optical filter controller 405 may read the information stored in the synchronizing information storage 403, and control the optical filter section 224 based on the read information. In this case, it is necessary to transmit all the synchronizing signals from the video display apparatus 100 to the video viewing glasses 120 constantly in response to a switching operation of video frames. Further, it is desirable for the video viewing glasses 120 to receive all the transmitted synchronizing signals. However, there is a case that all the signals are not successfully transmitted or received. For instance, in the case where a remote controller (remote controlling device) (not shown) as an accessory part of the video display apparatus 100 transmits data (data for turning on/off the power source of the video display apparatus 100, or data for causing the video display apparatus 100 to perform other predetermined operation) to the video display apparatus 100 using infrared light, the infrared light from the remote controller, and the infrared light for use in transmitting and receiving a synchronizing signal between the video display apparatus 100 and the video viewing glasses 120 may interact with each other, and the video viewing glasses 120 may fail to properly receive the synchronizing signal.

FIG. 12 is a diagram showing data transmission of a remote controller. A transmission period 1201 shown in the section (A) in FIG. 12 means a period when data is transmitted from the remote controller to the video display apparatus 100. The section (B) in FIG. 12 shows an operation in the transmission period 1201. In transmitting certain data, the remote controller transmits the same data for several times. In the section (B) in FIG. 12, the remote controller transmits the same data three times during the transmission period 1201, in other words, transmits data 1202, 1203, and 1204 during the transmission period 1201. The data transmission from the remote controller includes a predetermined non-transmission period between transmission of one data and transmission of succeeding data. Thereby, the video display apparatus 100 is operable to perform a processing of, for example, identifying a boundary between the preceding data and the succeeding data.

If the transmission period 1201 of data from the remote controller, and a timing of transmitting a synchronizing signal from the video display apparatus 100 to the video viewing glasses 120 are overlapped, the video viewing glasses 120 may fail to properly receive the synchronizing signal. In this embodiment, the timing of transmitting a synchronizing signal from the video display apparatus 100 to the video viewing glasses 120 is adjusted as follows.

The transmission controller 305 in the video display apparatus 100 accumulates in advance information relating to the transmission period 1201 of the remote controller. In the example shown in FIG. 12, the transmission controller 305 holds in advance time information relating to a transmission time 1205 corresponding to the transmission period 1201 of data from the remote controller. The transmission controller 305 controls transmission of a synchronizing signal to the video viewing glasses 120 depending on the length of the transmission time 1205.

A synchronizing signal group 1206 exemplified in the section (C) in FIG. 12 includes synchronizing signals to be generated in correspondence to a left-eye frame and a right-eye frame. As illustrated in the section (C) in FIG. 12, the synchronizing signal transmitter 306 transmits a succeeding synchronizing signal group 1206 upon lapse of a predetermined time (transmission suspending period) after transmitting one synchronizing signal group 1206 under the control of the transmission controller 305. In the example shown in FIG. 12, an interval (transmission suspending period), which is defined as a period from a point of time when transmission of a synchronizing signal group 1206 is completed to a point of time when transmission of a succeeding synchronizing signal group 1206 is started, may equal to twice of the transmission period 1201 of data from the remote controller, or more. Thereby, a probability of overlapping data from the remote controller with data corresponding to a synchronizing signal is reduced, as compared with a case of continuously transmitting synchronizing signals.

Each one of the synchronizing signal groups 1206 includes plural synchronizing signals in synchronism with plural consecutive video frames, as shown in the section (D) in FIG. 12. In the example shown in FIG. 12, one synchronizing signal group 1206 includes two synchronizing signals corresponding to two left-eye frames, and two synchronizing signals corresponding to two right-eye frames. The numbers of synchronizing signals corresponding to left-eye video frames and right-eye video frames included in one synchronizing signal group 1206 are determined, based on the amount (degree of definiteness) of information included in an external synchronizing signal, which is minimally required for generating an internal synchronizing signal with, for example, the internal synchronizing signal generator 404 in the video viewing glasses 120.

As the transmission interval of the synchronizing signal groups 1206 is extended with respect to the transmission period of data from the remote controller, the probability of interaction between the synchronizing signal groups 1206 and data transmitted from the remote controller is lowered. The transmission interval of the synchronizing signal groups 1206 depends on the time length required for transmitting one synchronizing signal group 1206, in addition to the amount of information included in an external synchronizing signal, which is required for generating an internal synchronizing signal. In the case where a time required for transmitting one synchronizing signal group 1206 is extremely long, the probability of overlapping with transmission of data from the remote controller is increased.

The transmission controller 305 is operable to determine the transmission interval of the synchronizing signal groups 1206 based on the above various information, and controls the synchronizing signal transmitter 306 to transmit the synchronizing signal groups 1206 at the determined transmission interval. During a period from a point of time when one synchronizing signal group 1206 is transmitted to a point of time when a succeeding synchronizing signal group 1206 is transmitted, the video viewing glasses 120 is controlled based on an internal synchronizing signal generated by the internal synchronizing signal generator 404.

The video viewing glasses 120 receive the synchronizing signal groups 1206 from the video display apparatus 100 at a predetermined time interval.

The synchronizing signal analyzer 402 analyzes a synchronizing signal received by the external synchronizing signal receiver 400 and detected by the synchronizing signal detector 401. The synchronizing signal analyzer 402 analyzes information relating to timings (e.g. cycles) for controlling the left-eye optical filter 241 and the right-eye optical filter 242 of the optical filter section 224, as shown in the section (D) and the section (E) in FIG. 7. In the example shown in the section (D) and the section (E) in FIG. 7, the synchronizing signal analyzer 402 calculates an interval (A1) for operating the left-eye optical filter 241 corresponding to the left-eye frame, an interval (B1) for opening the left-eye optical filter 241 corresponding to the left-eye frame (increasing the amount of light to be transmitted), an interval (C1) from a point of time when the left-eye optical filter 241 corresponding to the left-eye frame is started to open to a point of time when the right-eye optical filter 242 corresponding to the right-eye frame is started to open, and an interval (D1) for opening the right-eye optical filter 242 corresponding to the right-eye frame, based on an interval for receiving the synchronizing signals (pulses or a pulse group).

The synchronizing signal analyzer 402 corresponds to a part of a program to be executed by the CPU 220. The above calculation processing by the synchronizing signal analyzer 402 may be achieved, for example, by causing the CPU 220 to acquire a time when the respective synchronizing signals are received from the clock 220 and measure an interval for receiving the synchronizing signals. The values measured by the CPU 220 may be stored in the synchronizing information storage 403.

The synchronizing signal analyzer 402 may calculate an average value of synchronizing signal receiving intervals acquired plural times within the synchronizing signal group 1206 to more accurately obtain the respective measured times of the intervals (A1), (B1), (Cl), and (D1). In this case, as the number of times to be measured is increased, precision on the value to be calculated by the synchronizing signal analyzer 402 is enhanced.

In the case where the operations of the optical filters 241 and 242 of the optical filter section 224 are determined in advance (e.g. a case that the operation frequency of the optical filter section 224 is limited to two kinds of frequencies i.e. 120 Hz and 100 Hz), the internal synchronizing signal generator 404 may select a predetermined operation frequency, based on the value calculated by the synchronizing signal analyzer 402 in the above-described manner. In this case, the frequency for operating the optical filter section 224 may be more accurately determined, based on the information relating to the acquired synchronizing signals and the predetermined operation frequency.

The predetermined operation frequency of the optical filter section 224 may be 120 Hz which is equal to two times of 60 Hz, in the case of NTSC frequency, because it is necessary to operate a left-eye frame and a right-eye frame each at a frequency of 60 Hz. Similarly to the above, the predetermined operation frequency of the optical filter section 224 may be 100 Hz in the case of PAL frequency. Alternatively the predetermined operation frequency of the optical filter section 224 may be, for example, 144 Hz or 96 Hz in the case of other frequency.

The internal synchronizing signal generator 404 internally generates a synchronizing signal in the video viewing glasses 120, based on time interval information, which is stored in the synchronizing information storage 403, relating to the interval (A1) for starting an operation of the left-eye optical filter 241 corresponding to the left-eye frame, the interval (B1) for opening the left-eye optical filter 241 corresponding to the left-eye frame (increasing the amount of light to be transmitted), the interval (C1) from a point of time when the left-eye optical filter 241 corresponding to the left-eye frame is started to open to a point of time when the right-eye optical filter 242 corresponding to the right-eye frame is started to open, and the interval (D1) for opening the right-eye optical filter 242 corresponding to the right-eye frame. The CPU 220 is operable to generate the synchronizing signal based on information of the clock 222.

The optical filter controller 405 operates the left-eye optical filter 241 and the right-eye optical filter 242 of the optical filter section 224 in accordance with an internal synchronizing signal generated by the internal synchronizing signal generator 404.

Thereby, even if the video viewing glasses 120 fail to constantly receive synchronizing signals from the video display apparatus 100, the video viewing glasses 120 is operable to control the optical filter section 224 in synchronism with a switching operation between a left-eye video and a right-eye video to be displayed on the video displayer 303 by generating an internal synchronizing signal, whereby the viewer is allowed to continuously view a stereoscopic video.

Preferably, the synchronizing signal analyzer 402 may analyze a synchronizing signal, which corresponds to left-eye or right-eye video frames, included in the synchronizing signal group 1206 to be transmitted from the video display apparatus 100. In this case, the video viewing glasses 120 are operable to generate an internal synchronizing signal, once the synchronizing signal group 1206 is received. In this case, preferably, the number of synchronizing signals (the number of video frames) included in the synchronizing signal group 1206 is equal to or larger than the number of synchronizing signals required for generating an internal synchronizing signal with the video viewing glasses 120. In other words, preferably, the synchronizing signal generator 304 or the transmission controller 305 may successively transmit synchronizing signals of at least the number equal to or larger than the number of synchronizing signals required for generating an internal synchronizing signal with the video viewing glasses 120.

In the case where the synchronizing signal analyzer 402 acquires a synchronizing signal from the external device, after the information relating to the intervals (A1), (B1), (Cl), and (D1) is acquired, the synchronizing signal analyzer 402 may calculate intervals (A1), (B1), (Cl), and (D1) again, and update the previously calculated values to the newly calculated values. As a result of performing this operation, the video viewing glasses 120 may quickly respond to a change in the frame rate of the video display apparatus 100.

In the case where the video viewing glasses 120 fail to receive a synchronizing signal from the video display apparatus 100 for a predetermined time (e.g. a case that the video viewing glasses 120 fail to receive a synchronizing signal for a time longer than the interval for transmitting one synchronizing signal group 1206), the optical filter controller 405 may control the optical filter section 224 to open both of the left-eye optical filter 241 and the right-eye optical filter 242. Thereby, the video viewing glasses 120 are operable to provide the viewer with at least a video displayed on the video displayer 303, even if the video viewing glasses 120 fail to receive a synchronizing signal.

As described above, the video display apparatus 100 transmits synchronizing signals at a predetermined time interval. Further, the video viewing glasses 120 generate an internal synchronizing signal based on the synchronizing signal received from the video display apparatus 100, and drives the optical filter section 224 based on the internal synchronizing signal. As a result of performing this operation, even in the case where the video display system 1 fails to transmit or receive a synchronizing signal, a video to be displayed on the video display apparatus 100, and an operation of the optical filter section 224 in the video viewing glasses 120 may be synchronized to each other, thereby allowing the viewer to continuously view the video.

In this embodiment, the synchronizing signal analyzer 402 measures and analyzes four intervals i.e. the interval (A1) for starting an operation of the optical filter 241 corresponding to the left-eye frame, the interval (B1) for opening the left-eye optical filter 241 corresponding to the left-eye frame (increasing the amount of light to be transmitted), the interval (C1) from a point of time when the left-eye optical filter 241 corresponding to the left-eye frame is started to open to a point of time when the right-eye optical filter 242 corresponding to the right-eye frame is started to open, and the interval (D1) for opening the right-eye optical filter 242 corresponding to the right-eye frame. The invention is not limited to the above. For instance, a time for opening the right-eye optical filter 242 corresponding to the right-eye frame may be measured, using a time interval from a point of time when the left-eye optical filter 241 corresponding to the left-eye frame is closed. Any method for calculating synchronizing information based on synchronizing signals to be received is applicable to the invention.

In this embodiment, the transmission controller 305 holds in advance the information relating to the transmission period 1201 of data from the remote controller. The invention is not limited to the above. For instance, the video display apparatus 100 may be provided with a part (not shown) for receiving data from the remote controller. The transmission controller 305 may acquire data relating to a data receiving time required for receiving data from the remote controller, from the part for receiving data from the remote controller, and calculate the data receiving time from the remote controller. The transmission controller 305 may calculate the data transmission period 1201 using a predetermined computation formula, based on the calculated data receiving time. In this case, even if an unknown remote controller is used, the video display apparatus 100 is operable to properly adjust the transmission interval of synchronizing signals by receiving data from the remote controller.

FIG. 13 is a diagram showing an example of a control operation, in the case where a video supposed to be visually recognized as a two dimensional video is displayed on the video displayer 303. FIG. 14 is a diagram showing an example of a video supposed to be visually recognized as a two dimensional video.

The respective frames shown in the section (A) in FIG. 13 are supposed to be visually recognized by both eyes. The respective frames shown in the section (A) in FIG. 13 may contain a video supposed to be visually recognized as a two dimensional video, like a video shown in FIG. 14, for example. As shown in FIG. 14, the respective frames may be time-sequentially switched one from the other, and the position of the object “A” to be displayed on a video in the respective frames may be changed time-sequentially. In this case, the video illustrated in FIGS. 13 and 14 becomes a moving picture video representing identical contents.

In the case where a video is a normal video (a video supposed to be visually recognized as a two dimensional video), as illustrated in FIGS. 13 and 14, it is not necessary to alternately operate the left-eye optical filter 241 and the right-eye optical filter 242 in the video viewing glasses 120, as shown in the example described referring to FIG. 7. The optical filter controller 405 controls the optical filter section 224 so that the amounts of light to be transmitted through the left-eye optical filter 241 and the right-eye optical filter 242 substantially equal to each other (a difference in the amount of light to be transmitted between the left-eye optical filter and the right-eye optical filter lies within a predetermined range). In the example shown in FIG. 13, the video display apparatus 100 transmits a first synchronizing signal 1300 and a second synchronizing signal 1301 every one frame. In the respective frames, the first synchronizing signal 1300 serves as a synchronizing signal for increasing the amount of light, which is used in controlling opening the left-eye optical filter 241 and the right-eye optical filter 242, and the second synchronizing signal 1301 serves as a synchronizing signal for decreasing the amount of light, which is used in controlling closing the left-eye optical filter 241 and the right-eye optical filter 242.

The internal synchronizing system described referring to FIG. 12 may be applicable to the example shown in FIGS. 13 and 14. Further alternatively, the synchronizing signal generator 304 may generate either one of the first synchronizing signal 1300 and the second synchronizing signal 1301, and the synchronizing signal transmitter 306 may successively transmit the generated synchronizing signals, in place of generating both of the first synchronizing signal 1300 and the second synchronizing signal 1301. In this case, the first synchronizing signal 1300 or the second synchronizing signal 1301 to be transmitted for the first time serves as a synchronizing signal to be used for a control operation of opening the optical filter section 224, and the first synchronizing signal 1300 or the second synchronizing signal 1301 to be transmitted following the transmitted synchronizing signal serves as a synchronizing signal to be used for a control operation of closing the optical filter section 224.

Second Embodiment

The second embodiment is different from the first embodiment only in a synchronizing signal to be transmitted from a video display apparatus 100 to video viewing glasses 120. Since the other configuration of the second embodiment is substantially the same as the corresponding configuration of the first embodiment, description thereof is omitted herein.

FIG. 15 is a diagram showing a control using three kinds of synchronizing signals different from each other. A video frame shown in the section (A) in FIG. 15 is a stereoscopic video which is supposed to be perceived as a three-dimensional video (see FIGS. 5 and 6). The example shown in FIG. 15 is different from the first embodiment only in the synchronizing signals shown in the section (B) in FIG. 15. The section (B) in FIG. 15 shows three kinds of synchronizing signals 1501, 1502, and 1503 having waveforms different from each other. Similarly to the pulse waveform described referring to FIG. 8, a synchronizing signal analyzer 402 discriminates the kind of synchronizing signal, based on a difference in pulse number or pulse width among the three kinds of the synchronizing signals. For instance, the synchronizing signal analyzer 402 is operable to identify a signal having two pulses in a predetermined time, as a synchronizing signal for opening a left-eye optical filter 241; identify a signal having four pulses in the predetermined time, as a synchronizing signal for opening a right-eye optical filter 242; and identify a signal having three pulses in the predetermined time, as a synchronizing signal for closing the left-eye optical filter 241 and the right-eye optical filter 242 in an opened state.

A synchronizing signal generator 304 generates the first synchronizing signal 1501, when display of a video in a left-eye frame is started, and then transmits the first synchronizing signal 1501 from a synchronizing signal transmitter 306 to the video viewing glasses 120. When an afterglow in the left-eye frame becomes equal to or lower than a predetermined level after display of the video in the left-eye frame is ended, the synchronizing signal generator 304 generates the third synchronizing signal 1502, which is then transmitted from the synchronizing signal transmitter 306 to the video viewing glasses 120. An optical filter controller 405 in the video viewing glasses 120 controls opening/closing of the left-eye optical filter 241 and the right-eye optical filter 242 of an optical filter section 224, based on the transmitted synchronizing signals 1501 and 1502.

Similarly to the control for the left-eye frame, the synchronizing signal generator 304 generates the second synchronizing signal 1503, when display of a video in a right-eye frame is started. When an afterglow in the right-eye frame becomes equal to or lower than a predetermined level after display of the video in the right-eye frame is ended, the synchronizing signal generator 304 generates the third synchronizing signal 1502, which is then transmitted from the synchronizing signal transmitter 306 to the video viewing glasses 120. The optical filter controller 405 in the video viewing glasses 120 controls opening/closing of the left-eye optical filter 241 and the right-eye optical filter 242 of the optical filter section 224, based on the transmitted synchronizing signals 1503 and 1502.

In this embodiment, synchronization between the video display apparatus 100 and the video viewing glasses 120 is retained, using the three kinds of the synchronizing signals 1501, 1502, and 1503. In particular, a common synchronizing signal (in the above example, the third synchronizing signal 1502) is used to control closing of the left-eye optical filter 241 and the right-eye optical filter 242 of the optical filter section 224 (decreasing the amounts of light to be transmitted through the left-eye optical filter 241 and the right-eye optical filter 242). Similarly to the first embodiment, the synchronizing signal generator 304 creates a blind condition that the left-eye optical filter 241 and the right-eye optical filter 242 of the optical filter section 224 are simultaneously closed to synchronize the blind period with a period when a switching operation between the left-eye frame and the right-eye frame on the video displayer 303 is performed. As a result of the control operation, the viewer is allowed to view a clear video.

The video viewing glasses 120 may easily discriminate whether the optical filter section 224 should be opened or closed when the video viewing glasses 120 receives a synchronizing signal for the first time because the signal waveform of the synchronizing signal for use in control of opening the optical filter section 224 is different from the signal waveform of the synchronizing signal for use in control of closing the optical filter section 224.

FIG. 16 is a diagram showing an example of a control for viewing a two-dimensional display image described referring to FIGS. 13 and 14, using the synchronizing signal for use in control of opening the optical filter section 224, and the synchronizing signal for use in control of closing the optical filter section 224 having waveforms different from each other, which have been described referring to FIG. 15. In the control exemplified in FIG. 16, the first synchronizing signal 1501 and the third synchronizing signal 1502 shown in FIG. 15 are used. The first synchronizing signal 1501 serves as a synchronizing signal for increasing the light amount for use in control of opening both of the left-eye optical filter 241 and the right-eye optical filter 242. Similarly to the example described referring to FIG. 15, the third synchronizing signal 1502 serves as a synchronizing signal for decreasing the light amount for use in control of closing both of the left-eye optical filter 241 and the right-eye optical filter 242. As shown in FIG. 16, the third synchronizing signal 1502 is transmitted after the first synchronizing signal 1501 is transmitted during a period when each of the frames is displayed. Thereby, the left-eye optical filter 241 and the right-eye optical filter 242 are substantially simultaneously controlled to be opened and closed in each of the frames. In the example shown in FIG. 16, the second synchronizing signal 1503 shown in FIG. 15 may be used as a synchronizing signal for increasing the light amount.

FIG. 17 is a diagram showing a control using four kinds of synchronizing signals having waveforms different from each other. A video frame shown in the section (A) in FIG. 17 is a stereoscopic video which is supposed to be perceived as a three-dimensional video (see FIGS. 5 and 6). Similarly to the pulse waveform described referring to FIG. 8, the synchronizing signal analyzer 402 discriminates the kind of synchronizing signal, based on a difference in pulse number or pulse width among four kinds of synchronizing signals. For instance, the synchronizing signal analyzer 402 is operable to identify a signal having two pulses in a predetermined time, as a synchronizing signal 1501 for opening the left-eye optical filter 241; identify a signal having four pulses in the predetermined time, as a synchronizing signal 1503 for opening the right-eye optical filter 242; identify a signal having three pulses in the predetermined time, as a synchronizing signal 1502 for closing the left-eye optical filter 241; and identify a signal having five pulses in the predetermined time, as a synchronizing signal 1504 for closing the right-eye optical filter 242.

As shown in FIG. 17, the video viewing glasses 120 may be synchronized with the video display apparatus 100 using the four kinds of the synchronizing signals 1501, 1502, 1503, and 1504. It should be noted that the synchronizing signals shown in FIG. 17 are indicated with the same reference numerals as the synchronizing signals shown in FIGS. 15 and 16 to simplify the comparison with the example described referring to FIGS. 15 and 16.

In the control shown in FIG. 17, the synchronizing signal generator 304 generates the first synchronizing signal 1501, when display of a video in a left-eye frame is started; and generates the third synchronizing signal 1502, when an afterglow in the left-eye frame becomes equal to or lower than a predetermined level after display of the video in the left-eye frame is ended.

The synchronizing signal generator 304 also generates the synchronizing signal 1503, when display of a video in a right-eye frame is started; and generates the fourth synchronizing signal 1504, when an afterglow in the right-eye frame becomes equal to or lower than a predetermined level after display of the video in the right-eye frame is ended.

It should be understood, similarly to the first embodiment, that timings for generating synchronizing signals to be used in this embodiment (a synchronizing signal for opening an optical filter and for closing an optical filter in synchronism with a left-eye frame and a right-eye frame) may be adjusted on the basis of, for example, display characteristics of the video displayer 303.

In the case where a two-dimensional video described referring to FIG. 16 is viewed, the fourth synchronizing signal 1504 shown in FIG. 17 may be used, in place of the third synchronizing signal 1502 shown in FIG. 16.

Third Embodiment

In the first and the second embodiments, the video display apparatus 100 displays a video for allowing the viewer to view a stereoscopic video. In this embodiment, a video display apparatus 100 displays a video for allowing the viewer to view two moving picture videos representing contents different from each other.

FIG. 18 is a diagram showing a control for allowing the viewer to view two moving picture videos representing contents different from each other. FIG. 19 is a diagram showing an example of videos in a first video frame and a second video frame shown in the section (A) in FIG. 18. In the section (A) in FIG. 18, a first video and a second video to be displayed on a video displayer 303 of the video display apparatus 100 are switched every one frame. In the control shown in FIG. 18, the synchronizing signals shown in FIG. 18 are indicated with the same reference numerals as those used in FIG. 15 because synchronizing signals to be transmitted from the video display apparatus 100 are substantially the same as those described referring to FIG. 15.

The video display apparatus 100 displays a video by switching between the first video frame and the second video frame every one frame. During this control, as shown in FIG. 19, videos having no correlation to each other in contents are alternately displayed on a display panel 206. A synchronizing signal generator 304 generates synchronizing signals 1501, 1502, and 1503 as shown in the section (B) in FIG. 18 in the similar manner as described referring to FIG. 15. The synchronizing signal generator 304 generates the first synchronizing signal 1501 when display of a video in the first video frame is started; and generates the third synchronizing signal 1502 when an afterglow in the first video frame becomes equal to or lower than a predetermined level after display of the first video is ended. The generated first synchronizing signal 1501 and the generated third synchronizing signal 1502 are transmitted from the synchronizing signal generator 304 to an external synchronizing signal receiver 400 via a synchronizing signal transmitter 306.

Similarly to the control on the first video frame, the synchronizing signal generator 304 generates the second synchronizing signal 1503 when display of a video in the second video frame is started; and generates the third synchronizing signal 1502 when an afterglow in the second video frame becomes equal to or lower than a predetermined level after display of the second video is ended. The generated second synchronizing signal 1503 and the generated third synchronizing signal 1502 are transmitted from the synchronizing signal generator 304 to the external synchronizing signal receiver 400 via the synchronizing signal transmitter 306.

Video viewing glasses 120 are provided with a switch (not shown) so that the viewer may operate the switch to view one of a stereoscopic video, a first video, and a second video. In the case where the switch is operated to select the first video, a synchronizing signal analyzer 402 in the video viewing glasses 120 extracts solely synchronizing signals corresponding to the first video frame (i.e. the first synchronizing signal 1501 and the third synchronizing signal 1502) out of the received synchronizing signals.

The synchronizing signal analyzer 402 calculates information for generating an internal synchronizing signal, based on the extracted first synchronizing signal 1501 and the extracted third synchronizing signal 1502. An internal synchronizing signal generator 404 generates an internal synchronizing signal in synchronism with the first video frame, based on the calculated information, as shown in the section (C) in FIG. 18. An optical filter controller 405 operates an optical filter section 224, based on the internal synchronizing signal generated by the internal synchronizing signal generator 404.

The optical filter controller 405 controls the optical filter section 224 to open a left-eye optical filter 241 and a right-eye optical filter 242 for a period corresponding to the first video frame. On the contrary, the optical filter controller 405 controls the optical filter section 224 to close the left-eye optical filter 241 and the right-eye optical filter 242 for a period when the second video frame is displayed on the video displayer 303.

When the viewer operate the switch of the video viewing glasses 120 to select the second video, the synchronizing signal analyzer 402 in the video viewing glasses 120 extracts solely the second synchronizing signal 1503 and the third synchronizing signal 1502 corresponding to the second video frame out of the received synchronizing signals.

The synchronizing signal analyzer 402 calculates information for generating an internal synchronizing signal, based on the extracted second synchronizing signal 1503 and the extracted third synchronizing signal 1502. The internal synchronizing signal generator 404 generates an internal synchronizing signal in synchronism with the second video frame, based on the calculated information. The optical filter controller 405 operates the optical filter section 224, based on the internal synchronizing signal generated by the internal synchronizing signal generator 404.

The optical filter controller 405 controls the optical filter section 224 to open the left-eye optical filter 241 and the right-eye optical filter 242 for a period corresponding to the second video frame. On the contrary, the optical filter controller 405 controls the optical filter section 224 to close the left-eye optical filter 241 and the right-eye optical filter 242 for a period when the first video frame is displayed on the video displayer 303. As a result of the control operation, the viewer is allowed to selectively view solely the second video frame.

FIG. 20 is a diagram showing an example of videos to be visually recognized by the viewer through the control shown in FIG. 18. As described above, the viewer is allowed to visually recognize solely one of the first video and the second video through the control of the optical filter section 224. Accordingly, as shown in FIG. 20, the viewer is provided with a series of moving pictures correlated to each other in contents. When the first video is selected by using the switch of the video viewing glasses 120, the viewer is allowed to view the first video frame. On the other hand, when operating the switch of the video viewing glasses 120 to select the second video, the viewer is allowed to view the second video frame.

Alternatively, the control using two kinds of synchronizing signals described referring to FIG. 7 may be applied to the control shown in FIG. 18. In this case, for instance, the first synchronizing signal 700, 701 is allocated to the first video frame, and the second synchronizing signal 702, 703 is allocated to the second video frame. The synchronizing signal analyzer 402 extracts one of the first synchronizing signal 700, 701, and the second synchronizing signal 702, 703 in accordance with a switching operation with the switch of the video viewing glasses 120. The optical filter controller 405 is operable to control the optical filter section 224 to open/close the left-eye optical filter 241 and the right-eye optical filter 242, based on an extracted synchronizing signal out of the first synchronizing signal 700, 701, and the second synchronizing signal 702, 703.

Further alternatively, the control using four kinds of synchronizing signals described referring to FIG. 17 may be applied to the control shown in FIG. 18. In this case, for instance, the first synchronizing signals 1501 and the third synchronizing signal 1502 are allocated to the first video frame, and the second synchronizing signal 1503 and the fourth synchronizing signal 1504 are allocated to the second video frame. The synchronizing signal analyzer 402 extracts one of the paired signals constituted of the first synchronizing signal 1501 and the third synchronizing signal 1502, and the paired signals constituted of the second synchronizing signal 1503 and the fourth synchronizing signal 1504 in accordance with a switching operation with the switch of the video viewing glasses 120. The optical filter controller 405 is operable to control the optical filter section 224 to open/close the left-eye optical filter 241 and the right-eye optical filter 242, based on an extracted synchronizing signal pair, out of the paired signals constituted of the first synchronizing signal 1501 and the third synchronizing signal 1502, and the paired signals constituted of the second synchronizing signal 1503 and the fourth synchronizing signal 1504.

Similarly to the first embodiment, in this embodiment, an influence, for example, by afterglow may be reduced by controlling the left-eye optical filter 241 and the right-eye optical filter 242 of the optical filter section 224, based on display characteristics of the video displayer 303.

In the case where viewing a stereoscopic video is selected using the switch, as described in the first embodiment and the second embodiment, the viewer is allowed to view a stereoscopic image by controlling the optical filter section 224 in the video viewing glasses 120 in synchronism with a frame to be displayed on the video display apparatus 100.

In this embodiment, described is an example, wherein the user is allowed to view two different videos. The invention is not limited to the above. Similarly to the above, the viewer is allowed to selectively view three or more different videos in the similar manner as described above.

FIG. 21 is a diagram showing a control to be performed when a liquid crystal filter incorporated with a liquid crystal element is used as the optical filter section 224. The section (A) in FIG. 21 shows a left-eye frame and a right-eye frame to be switched. Similarly to the example shown in the section (A) in FIG. 15, in the example shown in the section (A) in FIG. 21, the left-eye frame and the right-eye frame are alternately switched. The section (B) in FIG. 21 shows a change in light emission luminance (i.e. afterglow characteristics) of the display panel 206. The section (C) in FIG. 21 shows external synchronizing signals 1502 and 1503 to be transmitted from the synchronizing signal transmitter 306. In the section (C) in FIG. 21, the synchronizing signals substantially equivalent to the second synchronizing signal 1503 and the third synchronizing signal 1502 shown in FIG. 15 are used. The second synchronizing signal 1503 is indicated by a waveform having two pulses, and the third synchronizing signal 1502 is indicated by a waveform having three pulses.

The section (D) and the section (E) in FIG. 21 show a control for video viewing glasses 120 equipped with a right-eye optical filter 242 having a standard response speed. In the case where the right-eye optical filter 242 having a standard response speed is used, in response to receiving the external synchronizing signal 1502, 1503, for instance, the internal synchronizing signal generator 404 generates an internal synchronizing signal 2102, 2103 substantially simultaneously with the external synchronizing signal 1502, 1503.

The section (F) and the section (G) in FIG. 21 show a control for video viewing glasses 120 equipped with a right-eye optical filter 242 having a response speed faster than the standard response speed. In the case where the right-eye optical filter 242 having a fast response speed is used, in response to receiving the external synchronizing signal 1502 by the external synchronizing signal receiver 400, for instance, the internal synchronizing signal generator 404 generates an internal synchronizing signal 2112 at a timing delayed by a predetermined delay time “D1” with respect to the external synchronizing signal 1502 to be used in control of opening the right-eye optical filter 242. The delay time “D1” may be a constant value inherent to the right-eye optical filter 242 to be used, or may be varied depending on the frequency of a frame. The delay time “D1” may be determined to such a value that the time when the opening rate of the right-eye optical filter 242 with a fast response speed reaches, for example, 50% may substantially correspond to the time when the opening rate of the right-eye filter 242 with a standard response speed reaches, for example, 50% after the external synchronizing signal 1502 is received.

Similarly to the above control, in the case where the external synchronizing signal receiver 400 receives the external synchronizing signal 1503, the internal synchronizing signal generator 404 generates the internal synchronizing signal 2112 at a timing delayed by a predetermined delay time “D2” with respect to the external synchronizing signal 1503 to be used in control of closing the right-eye optical filter 242. Similarly to the above, the delay time “D2” may be a value determined by any method, such as a predetermined inherent constant value, a value depending on the frequency of a frame, or a value determined so that the time when the right-eye optical filter 242 may be in a predetermined condition, for example, 50% of the opening rate corresponds to a predetermined condition for the right-eye filter 242 with a standard response speed, for example, 50% of the opening rate. The opening rate at 50% is merely an example. Alternatively, any combination such as combination of 50% and 30%, and combination of 80% and 90% may be used. In other words, any value for the opening rate may be applicable to the above-mentioned method utilizing the opening rate as a reference. In the case where the value for the opening rate is set to substantially 50%, image quality deterioration as an adverse effect resulting from offsetting the operation start timing may be suppressed.

In the case where a right-eye optical filter 242 having a standard response speed is used, the right-eye optical filter 242 is started to open before an afterglow in the left-eye frame is sufficiently reduced. As a result, the afterglow amount of a video in the left-eye frame, which is perceived by the viewer viewing a video through the right-eye optical filter 242 having a standard response speed, is increased.

In the case where a right-eye optical filter 242 having a fast response speed is used, the right-eye optical filter 242 is started to open after an afterglow in the left-eye frame is sufficiently reduced. As a result, less afterglow amount of a video in the left-eye frame may be perceived by the viewer who views the video through the right-eye optical filter 242 having a high response speed than a standard response speed.

Fourth Embodiment

In this embodiment, described is an arrangement as to how a transmission controller 305 controls transmission of synchronizing signals generated by a synchronizing signal generator 304.

FIG. 22 is a diagram showing a relation between an internal signal to be generated by the synchronizing signal generator 304, and a synchronizing signal to be transmitted by a synchronizing signal transmitter 306. The section (A) in FIG. 22 shows an internal signal to be generated by the synchronizing signal generator 304 in correspondence to a left-eye frame, the section (B) in FIG. 22 shows an internal signal to be generated by the synchronizing signal generator 304 in correspondence to a right-eye frame, and the section (C) in FIG. 22 shows a synchronizing signal to be outputted from the synchronizing signal transmitter 306.

The synchronizing signal generator 304 generates a synchronizing signal in the manner described in the first through the third embodiments. In generating a synchronizing signal, the synchronizing signal generator 304 internally generates and manages the signals as shown in the section (A) and the section (B) in FIG. 22. The example shown in the section (A) in FIG. 22 indicates that the synchronizing signal generator 304 determines that a video displayer 303 displays a left-eye frame so that the viewer may view or appropriately view it when the signal level of L signal is high. Specifically, in the section (A) in FIG. 22, a synchronizing signal 2209 is transmitted from the synchronizing signal transmitter 306 at a change 2201 in a signal level of L signal from low to high. Similarly to the above, in the section (A) in FIG. 22, a synchronizing signal 2210 for ending viewing of a left-eye frame is transmitted from the synchronizing signal transmitter 306 at a change 2202 in a signal level of L signal from high to low.

Similarly to the control on the left-eye frame, the example shown in the section (B) in FIG. 22 indicates that the synchronizing signal generator 304 determines that the video displayer 303 displays a right-eye frame so that the viewer may view or appropriately view it when the signal level of R signal is high.

The synchronizing signals in response to the end timing 2205 for the right-eye frame and the start timing 2201 for the left-eye frame are generated with a predetermined time interval, if the synchronizing signal generator 304 determines an appropriate display of the left-eye and the right-eye frame. The synchronizing signal transmitter may transmit the respective synchronizing signals in response to the respective end and start timings.

Control for a case opposite to the above, in which the end timing for a right-eye frame, and the start timing for a left-eye frame are generated with a shorter time interval than the predetermined time interval, is described in this embodiment.

The synchronizing signal generator 304 generates synchronizing signals in synchronism with a left-eye frame and a right-eye frame to be displayed on the video displayer 303 in accordance with its characteristics. The transmission controller 306 basically transmits the synchronizing signals to an external device, using various methods, based on synchronizing signals generated by the synchronizing signal generator 304. However, when the synchronizing signal transmitter 306 actually transmits synchronizing signals, it takes a certain time to transmit a synchronizing signal depending on a transmission system, a transmission protocol and so on. In general, the time required for transmitting a synchronizing signal by the synchronizing signal transmitter 306 is longer than a time required for internally generating a synchronizing signal by the synchronizing signal generator 304. Accordingly, even if the synchronizing signal generator 304 generates plural synchronizing signals in a short period, there is a case that the synchronizing signal transmitter 306 fails to transmit all the synchronizing signals within the period. In this embodiment, described is a configuration as to how the transmission controller 305 controls transmission of synchronizing signals.

Described is an example, wherein the synchronizing signal generator 304 generates synchronizing signals with a time relation between a signal level change timing 2207 shown in the section (B) in FIG. 22, and a signal level change timing 2203 shown in the section (A) in FIG. 22. The synchronizing signal generator 304 discriminates the viewing end timing 2207 for a right-eye frame and the viewing start timing 2203 for a left-eye frame consecutively or within a very short period. In this case, the synchronizing signal transmitter 306 may fail to follow the operation of the synchronizing signal generator 304 for the aforementioned reason. In view of this, in the case where two consecutive synchronizing signals exist in a predetermined time, in other words, in the case where a time interval between generation of a preceding synchronizing signal, and generation of a succeeding synchronizing signal is equal to or shorter than a predetermined time, the transmission controller 305 controls the synchronizing signal transmitter 306 to inhibit transmitting the succeeding signal.

In the case where the signal level change timings 2207 and 2203 have a relation as described above, the synchronizing signal generator 304 generates a synchronizing signal corresponding to a viewing end for a right-eye frame and a synchronizing signal corresponding to a viewing start for a left-eye frame, and the synchronizing signal transmitter 306 transmits a fourth synchronizing signal and a first synchronizing signal in this order, based on the generated synchronizing signals. However, in the case where the transmission controller 305 performs the above control, the transmission controller 305 controls the synchronizing signal transmitter 306 to transmit solely the fourth synchronizing signal to be transmitted firstly. Thereby, solely the fourth synchronizing signal is outputted from the video display apparatus 100.

Similarly to the above, in the case where the synchronizing signal generator 304 determines that a viewing end timing 2204 for a left-eye frame and a viewing start timing 2208 for a right-eye frame are generated within a predetermined time, the transmission controller 305 controls the synchronizing signal transmitter 306 to transmit solely a third synchronizing signal 2212, and suspend transmission of a second synchronizing signal corresponding to a viewing start for a right-eye frame.

Thereby, in the case where the synchronizing signal transmitter 306 fails to transmit a synchronizing signal to the external device with a time interval between synchronizing signals actually generated by the synchronizing signal generator 304, the transmission controller 305 prioritizes transmission of the preceding synchronizing signal, and suspends transmission of the succeeding synchronizing signal. As a result of the control operation, a synchronizing signal may not be transmitted from the video display apparatus 100 at an inappropriate timing.

It is desirable to properly operate video viewing glasses 120, based on the premise that the video display apparatus 100 performs the above-mentioned transmission of synchronizing signals. Accordingly, it is desirable for a synchronizing signal analyzer 402 in the video viewing glasses 120 to store information relating to, for example, a receiving time interval of synchronizing signals in an ordinary case, and compare the kind and the receiving time interval of actually received synchronizing signals, with the stored kind and receiving time interval of synchronizing signals to internally complement a synchronizing signal that has not been transmitted (received). The complementation may be performed, as described referring to FIG. 12, by storing the information relating to, for example, the kind and the receiving time interval of synchronizing signals in, for example, the synchronizing information storage 403 (memory 204), and generating an internal synchronizing signal in the video viewing glasses 120 with the internal synchronizing signal generator 404 and so on. Thereby, even in the case where the video display apparatus 100 fails to transmit a synchronizing signal at a proper timing, in other words, plural synchronizing signals are required to be transmitted within a predetermined period, synchronization between the video display apparatus 100 and the video viewing glasses 120 may be properly secured.

It is further preferable to implement an improved method for transmitting synchronizing signals, based on the premise that the video display apparatus 100 performs synchronizing signal transmission as described in this embodiment, and the video viewing glasses 120 perform a control in correspondence to the synchronizing signal transmission. For instance, the video display apparatus 100 transmits synchronizing signals with an identical time interval for at least a predetermined number of times (e.g. N times). Specifically, in the case where a cycle constituted of a viewing start for a left-eye frame, a viewing end for the left-eye frame, a viewing start for a right-eye frame, and a viewing end for the right-eye frame is defined as one set, the video display apparatus 100 transmits synchronizing signals with an identical time interval (transmission cycle) for at least N times. In this case, even if there is a synchronizing signal that has not been transmitted, as described in this embodiment, the video display apparatus 100 repeatedly transmits synchronizing signals in the same state (state that there is a synchronizing signal that is not transmitted) for at least N times. Thereby, the video viewing glasses 120 are allowed to generate an internal synchronizing signal with high precision. The video viewing glasses 120 change the control of an optical filter section by successively receiving the same information on the kind and the receiving time interval of synchronizing signals for a predetermined number of times. The predetermined number of times in this case is preferably a number of times equal to or smaller than N times, if the video display apparatus 100 transmits information on the same state for N times.

The contents recited in the first through the fourth embodiments are not limited to the foregoing embodiments. For instance, a processing to be executed by hardware may be executed using software to be executed on a CPU. Contrary to the above, a processing of software to be executed by a CPU may be executed using hardware.

The aforementioned embodiments mainly include the features of the above-mentioned embodiment having the following configurations.

A video display apparatus according to an aspect of the above-mentioned embodiment is adapted to display a video to be viewed through video viewing glasses. The video display apparatus includes: a display section for displaying the video; a synchronizing signal generator for generating an external synchronizing signal for notifying the video viewing glasses of an end of displaying a frame constituting the video in synchronism with the video; and a synchronizing signal transmitter for transmitting the external synchronizing signal.

In the above configuration, a signal indicating an end of displaying a frame constituting a video may be transmitted.

In the above configuration, the external synchronizing signal may be used in control of closing an optical filter section of the video viewing glasses. Thereby, the optical filter section of the video viewing glasses may be closed in correspondence to an end of displaying a frame.

In the above configuration, the synchronizing signal generator may generate the external synchronizing signal based on a display characteristic of the display section. Thereby, a signal indicating an end of displaying a frame constituting a video may be transmitted based on the display characteristics of the display section.

In the above configuration, the display characteristic of the display section may be an afterglow characteristic. Thereby, a signal indicating an end of displaying a frame constituting a video may be transmitted based on the afterglow characteristic.

In the above configuration, the display section may be a plasma display panel. Thereby, a signal indicating an end of displaying a frame constituting a video may be transmitted based on the afterglow characteristics of the plasma display panel.

In the above configuration, the video display apparatus may further include a transmission controller, wherein the transmission controller may control the synchronizing signal transmitter to transmit a synchronizing signal group comprising a plurality of the external synchronizing signals included in a predetermined time. In this configuration, the synchronizing signal transmitter may transmit one of the synchronizing signal groups under a control of the transmission controller a predetermined time after the other one of the synchronizing signal groups is transmitted under a control of the transmission controller. In this configuration, the video display apparatus may further include a remote controlling device for transmitting data for causing the video display apparatus to perform a predetermined operation to the video display apparatus, wherein the predetermined time may equal twice of a time required for the remote controlling device to transmit the data, or more. Thereby, interference between a signal from the remote controlling device and a synchronizing signal to be transmitted from the video display apparatus may be prevented.

In the above configuration, the video may include a first video and a second video, the display section may switchingly display the first video and the second video with time, the synchronizing signal generator may generate two kinds of the external synchronizing signals for notifying a start of displaying a frame constituting the first video, an end of displaying the frame constituting the first video, a start of displaying a frame constituting the second video, and an end of displaying the frame constituting the second video, and waveforms of the two kinds of the external synchronizing signals may be different from each other. In this configuration, the two kinds of the external synchronizing signals may include a first synchronizing signal for notifying the start of displaying the frame constituting the first video, and the end of displaying the frame constituting the first video, and a second synchronizing signal for notifying the start of displaying the frame constituting the second video, and the end of displaying the frame constituting the second video. Thereby, a signal indicating a start and an end of displaying a frame may be transmitted, using the two kinds of the external synchronizing signals having waveforms different from each other.

In the above configuration, the synchronizing signal transmitter may transmit the first synchronizing signal, the first synchronizing signal, the second synchronizing signal, and the second synchronizing signal in this order, when contents of the first video and contents of the second video are different from each other.

In the above configuration, the video may include a first video and a second video, the display section may switchingly display the first video and the second video with time, the synchronizing signal generator may generate three kinds of the external synchronizing signals for notifying a start of displaying a frame constituting the first video, an end of displaying the frame constituting the first video, a start of displaying a frame constituting the second video, and an end of displaying the frame constituting the second video, and waveforms of the three kinds of the external synchronizing signals are different from each other.

In this arrangement, the three kinds of the external synchronizing signals may include a first synchronizing signal for notifying the start of displaying the frame constituting the first video, a second synchronizing signal for notifying the start of displaying the frame constituting the second video, and a third synchronizing signal for notifying the end of displaying the frame constituting the first video and the end of displaying the frame constituting the second video. Thereby, a signal indicating a start and an end of displaying a frame may be transmitted, using solely the three kinds of the external synchronizing signals having waveforms different from each other.

In the above configuration, the synchronizing signal transmitter may transmit the first synchronizing signal, the third synchronizing signal, the second synchronizing signal, and the third synchronizing signal in this order, when contents of the first video and contents of the second video are different from each other. In this configuration, the synchronizing signal transmitter may transmits solely one of the first synchronizing signal, the second synchronizing signal, and the third synchronizing signal, in the case where contents of the first video and contents of the second video are identical to each other, or in the case where the video to be displayed on the display section is constituted solely of the first video. Thereby, a signal indicating a period when a video of good quality is displayed may be transmitted.

In the above configuration, the video may include a first video and a second video, the display section may switchingly display the first video and the second video with time, the synchronizing signal generator may generate four kinds of the external synchronizing signals for notifying a start of displaying a frame constituting the first video, an end of displaying the frame constituting the first video, a start of displaying a frame constituting the second video, and an end of displaying the frame constituting the second video, and wavefoinis of the four kinds of the external synchronizing signals may be different from each other. In this configuration, the four kinds of the external synchronizing signals may include a first synchronizing signal for notifying the start of displaying the frame constituting the first video, a second synchronizing signal for notifying the start of displaying the frame constituting the second video, a third synchronizing signal for notifying the end of displaying the frame constituting the first video, and a fourth synchronizing signal for notifying the end of displaying the frame constituting the second video. Thereby, a signal indicating a start and an end of displaying a frame may be transmitted, using solely the four kinds of the external synchronizing signals having waveforms different from each other.

In the above configuration, the synchronizing signal transmitter may transmit the first synchronizing signal, the third synchronizing signal, the second synchronizing signal, and the fourth synchronizing signal in this order, when contents of the first video and contents of the second video are different from each other. In this configuration, the synchronizing signal transmitter transmits solely one of the first synchronizing signal, the second synchronizing signal, the third synchronizing signal, and the fourth synchronizing signal, in the case where contents of the first video and contents of the second video are identical to each other, or in the case where the video to be displayed on the display section is constituted solely of the first video. Thereby, a signal indicating a period when a video of good quality is displayed may be transmitted.

Video viewing glasses according to another aspect of the above embodiment include: a synchronizing signal receiver for receiving an external synchronizing signal for notifying an end of displaying a frame constituting a video in synchronism with the video; an optical filter section including a pair of optical filters for adjusting amounts of light to be transmitted to a left eye and a right eye of a viewer, respectively; and an optical filter controller for controlling the optical filter section based on the external synchronizing signal.

According to the above configuration, the viewer may be provided with a video of good quality.

In the above configuration, the optical filter controller may control the optical filter section based on the external synchronizing signal to close one of the optical filters so that both of the optical filters are closed for a predetermined period until the other of the optical filters is opened. Thereby, the viewer may be provided with a video of good quality.

In the above configuration, the video viewing glasses may further include an internal synchronizing signal generator for generating an internal synchronizing signal based on the external synchronizing signal, wherein the optical filter controller may control the optical filter section, using the internal synchronizing signal based on the external synchronizing signal. Thereby, control of the optical filter section may be continued even while the external synchronizing signal is not received.

In the above configuration, the optical filter controller may control the optical filter section to close both of the optical filters for the predetermined period, based on the internal synchronizing signal. Thereby, a period when the light amount is suppressed may be continuously created even while the external synchronizing signal is not received.

In the above configuration, the optical filter controller may control the optical filter section, based on the internal synchronizing signal and a characteristic of the optical filters. Thereby, the viewer may be provided with a clear video without depending on the performance of an optical filter.

In the above configuration, the external synchronizing signal may include a first external synchronizing signal and a second external synchronizing signal having waveforms different from each other. In this configuration, the optical filter controller may control the optical filter section to close the one of the optical filters based on the first external synchronizing signal upon receiving the first external synchronizing signal by the external synchronizing signal receiver after the one of the optical filters is controlled so as to be opened, and the optical filter controller may control the optical filter section to close the other of the optical filters based on the second external synchronizing signal upon receiving the second external synchronizing signal by the external synchronizing signal receiver after the other of optical filters is controlled so as to be opened. Thereby, control of the optical filter section may be performed with use of solely the two kinds of the synchronizing signals having waveforms different from each other.

In the above configuration, the external synchronizing signal may include a first external synchronizing signal, a second external synchronizing signal, and a third synchronizing signal having waveforms different from each other. In this configuration, the optical filter section may control the optical filter section to open the one of the optical filters, based on the first external synchronizing signal, the optical filter section may control the optical filter section to open the other of the optical filters, based on the second external synchronizing signal, and the optical filter section may control the optical filter section to close both of the optical filters, based on the third external synchronizing signal.

In this configuration, the external synchronizing signal receiver may receive the external synchronizing signal in the order of the first external synchronizing signal, the third external synchronizing signal, the second external synchronizing signal, and the third external synchronizing signal. Thereby, control of the optical filter section may be performed, with use of solely the three kinds of the synchronizing signals having waveforms different from each other.

In the above configuration, the external synchronizing signal may include a first external synchronizing signal, a second external synchronizing signal, a third synchronizing signal, and a fourth external synchronizing signal having waveforms different from each other. In this configuration, the optical filter section may control the optical filter section to open the one of the optical filters, based on the first external synchronizing signal, the optical filter section may control the optical filter section to open the other of the optical filters, based on the second external synchronizing signal, the optical filter section may control the optical filter section to close the one of the optical filters, based on the third external synchronizing signal, and the optical filter section may control the optical filter section to close the other of the optical filters, based on the fourth external synchronizing signal. In this configuration, the external synchronizing signal receiver may receive the external synchronizing signal in the order of the first external synchronizing signal, the third external synchronizing signal, the second external synchronizing signal, and the fourth external synchronizing signal.

In the above configuration, the external synchronizing signal may include a plurality of the external synchronizing signals having waveforms different from each other, and the internal synchronizing signal generator may generate the internal synchronizing signal, based on a receiving time interval among the plurality of the external synchronizing signals. Thereby, control of the optical filter section may be continuously performed, even while the external synchronizing signal is not received.

A video system according to yet another aspect of the above embodiment is provided with a video display apparatus, and video viewing glasses for use in viewing a video displayed on the video display apparatus. The video display apparatus includes: a display section for displaying a video; a synchronizing signal generator for generating an external synchronizing signal for notifying an end of displaying a frame constituting the video in synchronism with the video; and a synchronizing signal transmitter for transmitting the external synchronizing signal to the video viewing glasses The video viewing glasses include: a synchronizing signal receiver for receiving the external synchronizing signal; an optical filter section having a pair of optical filters for adjusting amounts of light to be transmitted to a left eye and a right eye of a viewer, respectively; and an optical filter controller for controlling the optical filter section based on the external synchronizing signal.

The above configuration may prevent the viewer from viewing a video when a switching operation between frames is performed, and provide the viewer with a video of better quality.

This application is based on Japanese Patent Application No. 2009-097887 filed on Apr. 14, 2009, the contents of which are hereby incorporated by reference.

The embodiments or the examples described in the detailed description of the invention are provided to clarify the technical contents of the invention. The invention should not be construed to be limited to the embodiments or the examples. The invention may be modified in various ways as far as such modifications do not depart from the spirit and the scope of the invention hereinafter defined. 

1. A video display apparatus for displaying a video to be viewed through video viewing glasses, comprising: a display section for displaying the video; a synchronizing signal generator for generating an external synchronizing signal for notifying the video viewing glasses of an end of displaying a frame constituting the video in synchronism with the video; and a synchronizing signal transmitter for transmitting the external synchronizing signal.
 2. The video display apparatus according to claim 1, wherein the external synchronizing signal is used in control of closing an optical filter section of the video viewing glasses.
 3. The video display apparatus according to claim 1, wherein the synchronizing signal generator generates the external synchronizing signal based on a display characteristic of the display section.
 4. The video display apparatus according to claim 3, wherein the display characteristic of the display section is an afterglow characteristic.
 5. The video display apparatus according to claim 4, wherein the display section is a plasma display panel.
 6. The video display apparatus according to claim 1, further comprising a transmission controller, wherein the transmission controller controls the synchronizing signal transmitter to transmit a synchronizing signal group comprising a plurality of the external synchronizing signals included in a predetermined time.
 7. The video display apparatus according to claim 6, wherein the synchronizing signal transmitter transmits one of the synchronizing signal groups under a control of the transmission controller a predetermined time after the other one of the synchronizing signal groups is transmitted under a control of the transmission controller.
 8. The video display apparatus according to claim 7, further comprising a remote controlling device for transmitting data for causing the video display apparatus to perform a predetermined operation to the video display apparatus, wherein the predetermined time equals twice of a time required for the remote controlling device to transmit the data, or more.
 9. The video display apparatus according to claim 1, wherein the video includes a first video and a second video, the display section switchingly displays the first video and the second video with time, the synchronizing signal generator generates two kinds of the external synchronizing signals for notifying a start of displaying a frame constituting the first video, an end of displaying the frame constituting the first video, a start of displaying a frame constituting the second video, and an end of displaying the frame constituting the second video, and waveforms of the two kinds of the external synchronizing signals are different from each other.
 10. The video display apparatus according to claim 9, wherein the two kinds of the external synchronizing signals include a first synchronizing signal for notifying the start of displaying the frame constituting the first video, and the end of displaying the frame constituting the first video, and a second synchronizing signal for notifying the start of displaying the frame constituting the second video, and the end of displaying the frame constituting the second video.
 11. The video display apparatus according to claim 10, wherein the synchronizing signal transmitter transmits the first synchronizing signal, the first synchronizing signal, the second synchronizing signal, and the second synchronizing signal in this order, when contents of the first video and contents of the second video are different from each other.
 12. The video display apparatus according to claim 1, wherein the video includes a first video and a second video, the display section switchingly displays the first video and the second video with time, the synchronizing signal generator generates three kinds of the external synchronizing signals for notifying a start of displaying a frame constituting the first video, an end of displaying the frame constituting the first video, a start of displaying a frame constituting the second video, and an end of displaying the frame constituting the second video, and waveforms of the three kinds of the external synchronizing signals are different from each other.
 13. The video display apparatus according to claim 12, wherein the three kinds of the external synchronizing signals include a first synchronizing signal for notifying the start of displaying the frame constituting the first video, a second synchronizing signal for notifying the start of displaying the frame constituting the second video, and a third synchronizing signal for notifying the end of displaying the frame constituting the first video and the end of displaying the frame constituting the second video.
 14. The video display apparatus according to claim 13, wherein the synchronizing signal transmitter transmits the first synchronizing signal, the third synchronizing signal, the second synchronizing signal, and the third synchronizing signal in this order, when contents of the first video and contents of the second video are different from each other.
 15. The video display apparatus according to claim 13, wherein the synchronizing signal transmitter transmits solely one of the first synchronizing signal, the second synchronizing signal, and the third synchronizing signal, in the case where contents of the first video and contents of the second video are identical to each other, or in the case where the video to be displayed on the display section is constituted solely of the first video.
 16. The video display apparatus according to claim 1, wherein the video includes a first video and a second video, the display section switchingly displays the first video and the second video with time, the synchronizing signal generator generates four kinds of the external synchronizing signals for notifying a start of displaying a frame constituting the first video, an end of displaying the frame constituting the first video, a start of displaying a frame constituting the second video, and an end of displaying the frame constituting the second video, and waveforms of the four kinds of the external synchronizing signals are different from each other.
 17. The video display apparatus according to claim 16, wherein the four kinds of the external synchronizing signals include a first synchronizing signal for notifying the start of displaying the frame constituting the first video, a second synchronizing signal for notifying the start of displaying the frame constituting the second video, a third synchronizing signal for notifying the end of displaying the frame constituting the first video, and a fourth synchronizing signal for notifying the end of displaying the frame constituting the second video.
 18. The video display apparatus according to claim 17, wherein the synchronizing signal transmitter transmits the first synchronizing signal, the third synchronizing signal, the second synchronizing signal, and the fourth synchronizing signal in this order, when contents of the first video and contents of the second video are different from each other.
 19. The video display apparatus according to claim 17, wherein the synchronizing signal transmitter transmits solely one of the first synchronizing signal, the second synchronizing signal, the third synchronizing signal, and the fourth synchronizing signal, in the case where contents of the first video and contents of the second video are identical to each other, or in the case where the video to be displayed on the display section is constituted solely of the first video.
 20. Video viewing glasses comprising: a synchronizing signal receiver for receiving an external synchronizing signal for notifying an end of displaying a frame constituting a video in synchronism with the video; an optical filter section including a pair of optical filters for adjusting amounts of light to be transmitted to a left eye and a right eye of a viewer, respectively; and an optical filter controller for controlling the optical filter section based on the external synchronizing signal.
 21. The video viewing glasses according to claim 20, wherein the optical filter controller controls the optical filter section based on the external synchronizing signal to close one of the optical filters so that both of the optical filters are closed for a predetermined period until the other of the optical filters is opened.
 22. The video viewing glasses according to claim 21, further comprising an internal synchronizing signal generator for generating an internal synchronizing signal based on the external synchronizing signal, wherein the optical filter controller controls the optical filter section, using the internal synchronizing signal based on the external synchronizing signal.
 23. The video viewing glasses according to claim 22, wherein the optical filter controller controls the optical filter section to close both of the optical filters for the predetermined period, based on the internal synchronizing signal.
 24. The video viewing glasses according to claim 22, wherein the optical filter controller controls the optical filter section, based on the internal synchronizing signal and a characteristic of the optical filters.
 25. The video viewing glasses according to claim 21, wherein the external synchronizing signal includes a first external synchronizing signal and a second external synchronizing signal having waveforms different from each other.
 26. The video viewing glasses according to claim 25, wherein the optical filter controller controls the optical filter section to close the one of the optical filters based on the first external synchronizing signal upon receiving the first external synchronizing signal by the external synchronizing signal receiver after the one of the optical filters is controlled so as to be opened, and the optical filter controller controls the optical filter section to close the other of the optical filters based on the second external synchronizing signal upon receiving the second external synchronizing signal by the external synchronizing signal receiver after the other of optical filters is controlled so as to be opened.
 27. The video viewing glasses according to claim 21, wherein the external synchronizing signal includes a first external synchronizing signal, a second external synchronizing signal, and a third synchronizing signal having waveforms different from each other.
 28. The video viewing glasses according to claim 27, wherein the optical filter section controls the optical filter section to open the one of the optical filters, based on the first external synchronizing signal, the optical filter section controls the optical filter section to open the other of the optical filters, based on the second external synchronizing signal, and the optical filter section controls the optical filter section to close both of the optical filters, based on the third external synchronizing signal.
 29. The video viewing glasses according to claim 26, wherein the external synchronizing signal receiver receives the external synchronizing signal in the order of the first external synchronizing signal, the third external synchronizing signal, the second external synchronizing signal, and the third external synchronizing signal.
 30. The video viewing glasses according to claim 21, wherein the external synchronizing signal includes a first external synchronizing signal, a second external synchronizing signal, a third synchronizing signal, and a fourth external synchronizing signal having waveforms different from each other.
 31. The video viewing glasses according to claim 28, wherein the optical filter section controls the optical filter section to open the one of the optical filters, based on the first external synchronizing signal, the optical filter section controls the optical filter section to open the other of the optical filters, based on the second external synchronizing signal, the optical filter section controls the optical filter section to close the one of the optical filters, based on the third external synchronizing signal, and the optical filter section controls the optical filter section to close the other of the optical filters, based on the fourth external synchronizing signal.
 32. The video viewing glasses according to claim 31, wherein the external synchronizing signal receiver receives the external synchronizing signal in the order of the first external synchronizing signal, the third external synchronizing signal, the second external synchronizing signal, and the fourth external synchronizing signal.
 33. The video viewing glasses according to claim 20, wherein the external synchronizing signal includes a plurality of the external synchronizing signals having waveforms different from each other, and the internal synchronizing signal generator generates the internal synchronizing signal, based on a receiving time interval among the plurality of the external synchronizing signals.
 34. A video system provided with a video display apparatus, and video viewing glasses for use in viewing a video displayed on the video display apparatus, the video display apparatus including: a display section for displaying a video; a synchronizing signal generator for generating an external synchronizing signal for notifying an end of displaying a frame constituting the video in synchronism with the video; and a synchronizing signal transmitter for transmitting the external synchronizing signal to the video viewing glasses, and the video viewing glasses including: a synchronizing signal receiver for receiving the external synchronizing signal; an optical filter section having a pair of optical filters for adjusting amounts of light to be transmitted to a left eye and a right eye of a viewer, respectively; and an optical filter controller for controlling the optical filter section based on the external synchronizing signal. 